Symptoms
Hoxhunt add-in and other add-ins display a generic "two cubes" icon.
Explanation
Do not save unencrypted files to disk has been set to value enabled.
Office add-ins are thus unable to store add-in graphics to your computer.
NOTE: This is a symptom for Office add-ins only, as they are loaded from your Exchange service when Outlooks is started. It doesn't occur for stand-alone COM/VSTO add-ins that are installed locally on your computer.
Resolution
Open Internet Options and make sure Do not save encrypted files to disk is set to not configured or (0). Incorrect value is enabled.
If you are unable to change the setting, please ask assistance from your IT team. Tell them that "Do not save unencrypted files to disk" has been set to value enabled in IE's GPO settings, and the correct value is not configured or 0.
Disclaimer
If your company has a Hoxhunt button with a custom logo design and the above doesn't fix the problem, please contact Hoxhunt Support. There might be an issue with the hosting of your custom graphics assets. Please refer to this KB article when contacting Support.