Can't save files on Mac desktop with 365 Excel or Word but I can on my Mac laptop

The desktop Mac likely has an Excel/Word saving problem caused by either:

• Office for Mac not being fully updated after being off for a long period
• A disk/permissions or temporary-file issue that interrupts the save process

Use these steps on the desktop Mac (not the laptop):

1. Update Office for Mac
   • Open Word or Excel on the desktop Mac.
   • On the Help menu, select Check for Updates.
   • Set How would you like to check for software updates? to Automatically and choose a frequency.
   • Select Check for Updates and install any available updates.
   • Restart Word/Excel and test saving again.
2. Test saving to a different location
   • In Word/Excel, open a file.
   • Select File > Save As.
   • Try saving to:
     • A different folder on the Mac (for example, Documents instead of Desktop), and
     • An online location such as OneDrive or SharePoint using Online Locations in the Save As dialog.
   • If saving works to OneDrive or another folder but not to the original location, the issue is likely with that specific folder or drive (permissions, disk, or connection).
3. Check for disk/permissions issues
   If saving still fails, the problem may be with how Office creates temporary files during save (for example, “serious disk error” or similar messages). In that case:
   • Ensure the desktop Mac’s primary drive has free space and is not write-protected.
   • Try saving the same file to an alternative drive or location (external disk, different folder). If that works, the original location has a permissions or disk problem.

If, after updating Office and testing alternate locations, saving still fails on the desktop but not on the laptop, contact Microsoft Support for further investigation, as the issue is likely environmental on that Mac (disk, OS, or profile-specific).

References:

• Save a file in Office for Mac
• There is a serious disk error on when attempting to save, copy and paste or create auto recovery files in Office for Mac
• Troubleshoot why Excel doesn't save changes