open xlsx files in Microsoft 365 Personal

Follow these checks and steps in order:

1. Confirm that Excel can open .xlsx files in general
   Create a new blank workbook in Excel, save it as .xlsx, close it, and reopen it.
   • If this fails, the Excel installation is likely damaged → go to step 4.
2. Check if the problem is specific to certain files (possible corruption or format issue)
   If only some previously created files fail to open:
   • If they are stored in SharePoint/OneDrive, download a copy to the local PC and try again.
   • If the file opened previously but now does not, it may be corrupted or saved in a format that is not compatible with the current apps. In that case, follow the repair guidance:
     • Use the methods in “Repairing a corrupted workbook” and “Open a document after a file corruption error” to try to recover the file.
   • When sharing or moving files between devices, ensure they are saved and reopened in the same format (for example, .xls stays .xls, .xlsx stays .xlsx).
3. Check file type and platform support
   If trying to open files on mobile (for example, iOS):
   • .xlsx and .xlsm can be opened and edited.
   • Older or special formats (such as .xlsb, .csv, .xltx, .xls, etc.) may open only as read-only or not be editable.
     If the file is in a format that is read-only on that platform, open it on a supported desktop Excel app instead.
4. Repair or update Office if Excel itself is failing
   If Excel shows errors like “Excel has run into an error that is preventing it from working correctly” or crashes when opening any file:
   • Run an Online Repair of Microsoft 365 from Windows Settings → Apps → Installed apps → Microsoft 365 → Modify → Online Repair, then restart the PC and test again.
   • If the issue started after an OS upgrade (for example, Windows 7 → Windows 10) and the error says the file is corrupt or cannot be opened, install the latest Office updates as described in “Errors opening Office files after upgrading from Windows 7 to Windows 10”.
5. Ensure the correct Office version and license are active
   • If another Office version (for example, an old Office 2016 or institutional install) is still present, files may open in that version and be read-only or unlicensed.
   • Open Excel, go to File → Account, and:
     • Use Switch License or Update license and sign in with the account that has the Microsoft 365 Personal subscription.
   • If the apps show a “subscription canceled” or similar message, verify the subscription status at the Microsoft account page and make sure the same account is used in Excel.
6. If files are from SharePoint/OneDrive and suddenly all stopped opening
   • There may be corruption or version issues. Download the affected workbook, then follow the corruption-repair steps mentioned in step 2.

If after these steps Excel still cannot open any .xlsx files, the next actions are to fully repair Office (step 4) and verify that no older or conflicting Office installation is taking over file associations (step 5).

References:

• Fix problems opening documents in SharePoint libraries
• Why can't I open my Excel file?
• Errors opening Office files after upgrading from Windows 7 to Windows 10
• Double-clicking an Office file fails to open it in the correct Office program
• When I open an excel file it shows - We're sorry, but excel has run into an error that is preventing it from working correctly, Excel will need to be closed as a result. would you like us to repair now? then shows the option "repair now","help","close" - Microsoft Q&A
• When opening Word or Excel, getting a 'subscription canceled' message but I have renewed my Office subscription - Microsoft Q&A
• Can't get Office 365 to run because of pre-existing Office 2016 - Microsoft Q&A
• Excel files now not opening. - Microsoft Q&A