If you see a red unlock in the User Activity Log, it will also show an error code.
Click on the orange icon in the ERROR column to open the User Activity Error Code Guide.
This guide will help you identify many of your end user issues and provide a suggested action for each code.
Keep in mind, your organization selected Vitrium to control access to your content so many of the errors are situations where the user has reached or exceeded some limit you have set in your DRM policy.
If you have an integration with your Vitrium account, you may see custom messages that are not listed in the User Activity Error Code Guide instead. In these cases, refer to your internal documentation or connect with the dev team(s) that assisted with the integration for further information.
Our tutorial video on our User Activity Log has a section covering this Error Code Guide, starting at 2:12.