Overview

Some Outlook users may receive an add-in error when using the "Report this email" button. ADD-IN ERROR is an error that usually occurs before Hoxhunt add-in even starts to initialize. However, it may occur in different scenarios when using Web Outlook. There are many variations of the error, and this article aims to describe many of them.

Microsoft's documentation:  https://docs.microsoft.com/en-us/office/troubleshoot/error-messages/apps-for-office-not-start

Most common ADD-IN ERROR

PROBLEM

ADD-IN ERROR
This add-in could not be started. Close this dialog to ignore the problem or click "Restart" to try again.

EXPLANATION

This is often related to a disabled feature called Protected Mode which is controlled by your computer's security settings or your organisation's group policy.

SOLUTION #1

1. Open Internet Options (press Windows key + R, type inetcpl.cpl and press Enter key).
2. Select Security tab.
3. Select Internet from the available zones.
4. Tick Enable Protected Mode and click OK.
5. Relaunch Outlook and try again.

SOLUTION #2

If the error persists:

1. Open Internet Options (press Windows key + R, type inetcpl.cpl and press Enter key).
2. Select Security tab.
3. Select Restricted sites from the available zones.
4. Tick Enable Protected Mode.
5. Relaunch Outlook and try again.

SOLUTION #3

If the error persists:

1. Open Internet Options (press Windows key + R, type inetcpl.cpl and press Enter key).
2. Select Security tab.
3. Select Trusted sites from the available zones.
4. Tick Enable Protected Mode.
5. Click Sites button.
6. Enter *.hoxhunt.com to the list.
7. Relaunch Outlook and try again.

SOLUTION #4

If the error still persists, check Event Viewer for crashes:

1. Open Event Viewer.

2. Navigate to Windows Logs > Application and look for matching Outlook errors. If no errors are found, navigate to Applications and Services Logs > Microsoft Office Alerts, and look for matching Outlook errors.

Then refer to this article and apply the recommended fix: ADD-IN ERROR (due to corrupted Legacy Edge)

SOLUTION #5

If the error still persists:

This error can be caused by a rare bug in the installed WebView2 Runtime version. For example, in October 2021 Microsoft released a faulty version of the runtime (95.0.1020.30) that caused Outlook add-ins to crash for some users, displaying ADD-IN ERROR.

Microsoft released a fix in version 95.0.1020.40. Please make sure your WebView2 Runtime is up to date.

SOLUTION #6 (unverified)

Add-ins may not start when Attack Surface Reduction Rules are active in Microsoft Endpoint Manager. Please check this bug ticket for most recent information: https://github.com/OfficeDev/office-js/issues/1892

Enabling Protected Mode still has no effect, what's. going on?

Admin policies take priority over local settings. If enabling Protected Mode through Internet Explorer has no effect, or the ability to enable Protected Mode is turned off, check your admin settings to see if there's a Group Policy that disables Protected Mode.

Why should Protected Mode be enabled?

Microsoft Office Add-ins using the Office Add-in platform are designed to run in isolation, using a low right sandbox. Several features, such as the task pane view, use web views provided using Internet Explorer APIs.  To ensure these components execute HTML script in low rights mode, Office explicitly requires the browser object to run in Protected Mode.  Currently, IE does not support this from the API unless Protected Mode is enabled for Restricted Sites zone in IE itself.  This is typically not a problem since this is the default setting, and rarely will users disable it. However, if disabled (by user action or by GPO), these Office add-in types may report an error when starting and refuse to load. It is an expected failure under that condition, and is blocked for security reasons. More info here.

Other variations

PROBLEM

ADD-IN ERROR
This add-in seems to be having problems. Click "Restart" to try starting it again.

EXPLANATION

The web browser used by Outlook add-ins may be crashing. It is usually Chromium Edge. To confirm this, do the following:

1. Open Event Viewer application.

2. Go to Windows logs > Applications.

3. Look for recent Application crashes marked with a red cross symbol.

4. If the error event is occurring for msedge.exe (or a WebView process) and it corresponds to the time of the error, the add-in issue is caused by a crashing web browser or web runtime.

SOLUTION

Try to launch Chromium Edge manually. If it crashes, you need to reinstall Edge. Note that Repair install may not be enough. After successful re-installation, restart your computer and try Hoxhunt add-in again.

You may refer to for example: https://thegeekpage.com/microsoft-edge-wont-open/

IMPORTANT: Hoxhunt doesn't provide support for re-installing web browsers such as Chromium Edge. We don't take any responsibility about the third-party site's contents or potential mistakes.

NOTE: If re-installing Chromium Edge doesn't help and it's still crashing, you may need to re-install your Windows environment.

PROBLEM

ADD-IN ERROR
Add-ins are currently blocked to help to protect the security of your computer.
This add-in could not be started. Close this dialog to ignore the problem or click "Restart" to try again.

ADD-IN ERROR Something went wrong and we couldn't start this add-in. Please try again or contact your system administrator.

EXPLANATION

Same as above.

SOLUTION

Same as above.

PROBLEM

ADD-IN ERROR
This add-in is not approved for use within mailboxes that aren't managed by your organization.

EXPLANATION

Your organization doesn't allow to use Hoxhunt add-in in the selected mailbox.

SOLUTION

Move the email to a compatible mailbox and try using Hoxhunt again.

PROBLEM

ADD-IN ERROR
Sorry, we couldn't load the add-in because your version of Internet Explorer is not supported.
Click “See Details” for a list of supported browser versions.

ADD-IN ERROR
Sorry, we couldn't load the add-in because your browser version is not supported.
Click here for a list of supported browser versions.

ADD-IN ERROR
Sorry, we couldn't load the add-in because Internet Explorer is disabled.
Click “See Details” for more information.

EXPLANATION #1

You Outlook needs Internet Explorer to run Hoxhunt add-in but the version you have installed is too old.

SOLUTION #1

Update your IE to a newer version, or upgrade your Windows and/or Office so Hoxhunt add-in can be run in Microsoft Edge or Chromium Edge.

Read more about automatic browser selection for Office add-ins: https://docs.microsoft.com/en-us/office/dev/add-ins/concepts/browsers-used-by-office-web-add-ins

EXPLANATION #2

Internet Explorer is not installed or it has been disabled.

SOLUTION #2

Re-install / re-activate Internet Explorer.

1. Right Click the Start icon and select Control Panel

2. Click Programs

3. Choose Programs and Features

4. Click Turn Windows features on or off

5. Check the box next to Internet Explorer 11

6. Reboot Windows in order to finalize the changes and re-enable Internet Explorer.

EXPLANATION #3

Internet Explorer settings (in Internet Options) are corrupt.

SOLUTION #3

Reset Internet Explorer settings.

1. Open Internet Options (press Windows key + R, type inetcpl.cpl and press Enter key).
2. Select the Advanced tab.

3. In the Reset Internet Explorer Settings dialog box, select Reset.

4. In the box, Are you sure you want to reset all Internet Explorer settings?, select Reset.

5. When Internet Explorer finishes applying default settings, select Close, and then select OK. Restart your PC to apply changes.

PROBLEM

ADD-IN ERROR
Sorry, you seem to have lost your network and/or Internet
connection. Click "Retry" once you're back online.

ADD-IN ERROR
Sorry, we can't load the add-in. Please make sure you have network and/or Internet
connectivity. Click "Retry" once you're back online.

EXPLANATION

Most likely something is preventing access to *.hoxhunt.com. It can be local firewall software, VPN software, proxy configuration or Metered Connection setting.

SOLUTION

Please switch to another network connection and try again.

PROBLEM

ADD-IN ERROR
A problem occurred while trying to reach this add-in.

EXPLANATION

There might be a problem accessing the manifest URL (officejs.hoxhunt.com). Issue may be temporary (downtime on Hoxhunt side) or more permanent (proxy, firewall, Enterprise Mode etc. is blocking access).

SOLUTION

Please switch to another network connection and try again. Make sure proxy or firewall is not blocking access to officejs.hoxhunt.com.

Enable Protected Mode in Internet Options > Security > Trusted sites.

Add *.hoxhunt.com to the Sites list. Reboot and check if problem is fixed.

If problem is still not resolved, go to Internet Options > Advanced and disable TLS 1.0 and make sure to enable TLS 2.0.

PROBLEM

This add-in has been disabled to help keep you safe.
To continue using the add-in, validate that this item is hosted in a trusted domain or open it in the Office desktop app.

EXPLANATION

Running Office add-ins is prevented as a security measure. This error occurs only in Web Outlook (OWA) for on-premise Exchange Server customers.

SOLUTION

Please refer to this KB article for a solution: https://support.hoxhunt.com/hc/en-us/articles/360017226459

PROBLEM

Addon error
This addon is not approved for documents not maintained by this organisation. 
If you want to use it, save this document in place maintained by your organisation.
If you want more information, contact your administrator.

EXPLANATION

Root cause of this error is unverified. It may be related to Azure Information Protection.

SOLUTION

https://docs.microsoft.com/en-us/azure/information-protection/what-is-information-protection

PROBLEM

An add-on for this website failed to run.
Check the security settings in Internet Options for potential conflicts.

EXPLANATION

Some hoxhunt.com sites are listed on different Security zones.

SOLUTION

Make sure *.hoxhunt.com is listed in Trusted sites.
Make sure no hoxhunt.com addresses are listed in Restricted sites.

PROBLEM

EXPLANATION

This is most likely ADD-IN ERROR as well, although the error message is not displayed. Hover over or click the red-white cross symbol in hope the error message appears.