Do a test. Close Opera GX, open up a command prompt, type:
"%LocalAppData%\Programs\Opera GX\opera.exe" "--user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36"and press enter to launch Opera GX.
Then, goto the URL opera://browserjs and disable browser.js for the session.
Then, goto the URL opera://settings/content/all, type microsoft.com in the search field and click "Delete displayed data". Then repeat for other Microsoft domains like office.com and live.com. Whatever domains Teams uses.
Then, goto the URL opera://settings/clearBrowserData and clear "cached images and files" for all time.
Then, log in and test things to see if they now work.