Looking solution for Power BI does not loads up in the Microsoft Teams desktop app or Reports no longer showing in Microsoft Teams.
I would suggest trying https://teams.microsoft.com/ first and checking the results.
Additionally, sign out of Microsoft Teams completely and log back in, Teams then refresh the PowerBI tab.
Try to Clear Microsoft Teams Cache
Go to File Explorer, and type in %appdata%\Microsoft\teams
Under the directory, you’ll see a few of the following folders: Application Cache, Blob_storage, Cache, databases, and many more folders.
Under those folders delete all files and re-open Microsoft Teams.
For more details, follow this article’s 5th point – Clear Microsoft teams Cache Files
Check if the issue still persists, then follow the below solution.
Uninstall and Reinstall the Microsoft Teams
After uninstalling and re-installing the Microsoft Teams app, no further issue was found.
If you want you can follow this article to get in detailed – How to Uninstall and Reinstall Teams
I hope this helps, but please let me know which solution works for you or if you have any other questions.