Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
This usually happens when Office does not detect the original license after the repair/reinstall, or it is signed in with the wrong Microsoft account. It can also happen if an old trial or another Office version is still on the computer and is confusing activation.
Here are some suggestions you can try:
First, open Word or Excel and go to File, then Account. Sign out of all accounts, close Office, reopen it, and sign in with the same Microsoft account that was used to buy or activate Office. Then check Microsoft account Services and subscriptions to confirm your Office license appears there.
If the license is shown there, reinstall Office from that same page instead of using a random installer or trial prompt. That helps make sure the installed version matches your license.
Also check Windows Settings, then Apps, and remove any old Office, Microsoft 365 trial, or duplicate Office entries. It is recommended that old saved licenses or leftover trial versions can make Office keep asking to buy or activate again.
After that, restart the PC and open Office again. If it still asks you to buy Microsoft 365, run Microsoft’s activation troubleshooter or do an Online Repair from Settings, Apps, Microsoft Office, Modify, Online Repair.
For the saving problem, try saving a test file directly to Desktop or Documents. If it saves there, the issue may be with the folder or drive permissions, not Office itself.
Thank you for your patience in reading, I hope this information has been helpful to you.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment."
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.