Hi Irvin.
Thank you for the question.
Since this is my go-to response to this common problem, I shall mention it here - Try logging in at office.com. If that works, PowerPoint should sync automatically. If it doesn't, then we know the issue is account-specific over app. Some other fixes can be :
- Clearing out old sign-ins by heading to Windows settings > Accounts > Access work or school. If you see any outdated Microsoft accounts hanging around, remove them. Then try signing back in with the right one.
- Try a fresh browser session by clearing your cookies/cache or just open an InPrivate/Incognito window, if you are logging in through PowerPoint Online. Old session data can be culprits of such endless problem loops.
- Update your Office apps by opening any Office app. Go to Files > Account > Update Options > Update Now. This should help clear authentication bugs if any.
- Rule out the possibility of license not matching the app version by checking the account type. Also connect through mobile hotspot to rule out firewall blocks.
Hope this helps! Let me know in the comments if you have any further queries.