Hi @IBN ,
Are you able to access the Meeting Options page from the Calendar within the Teams app?
What's the build number of Teams and Outlook in your environment?
Based on your description, I tried checking it on my end and can successfully change the meeting options in Outlook:
Below are the version information for my Outlook and Teams app and you can compare them with yours:
For your situation, based on my experience, it could be a temporary backend issue, so you can ask one of the affected users to check it now and see how it goes. If the error is still there, as suggested by TKujala, it's recommended to manually check for updates by going to the ellipsis (...) menu next to their profile picture and selecting Check for updates. In case the issue persists, considering that clearing the Teams cache worked for you, you can check the link shared by TKujala to try deleting Teams cache for all users using script. Or you may share the article below to guide through the affected users to clear the Teams cache:
Clear the Teams cache on a Windows 10 PC
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