Unable to save Excel documents

Try these steps in order:

1. In Excel, select File > Save As and save the workbook with a new file name.
2. If that fails, try File > Save As and save it to another location, such as the local Mac drive instead of OneDrive or a network/external drive.
3. Create a new workbook and try saving it to the same location where the original file is stored. If the new workbook also fails to save there, the problem is likely with that location.
4. Check whether the file is in a location where only read access is available. Excel needs read, write, modify, and delete permissions to complete a save.
5. If the workbook is stored on OneDrive and was previously tied to Microsoft 365 cloud storage, download the file from OneDrive to the Mac and save it locally. If Files On-Demand is involved, keeping a local copy can help.
6. Make sure the destination has enough free space. If the disk is full, Excel cannot complete the save.
7. If the file path and name are very long, shorten them. Excel can show Filename is not valid if the full path exceeds 218 characters.
8. If antivirus software is running, temporarily deactivate it and test saving again, because antivirus scanning can interrupt Excel while it creates and renames the temporary save file.
9. If the problem affects one workbook only, try moving the sheets into a new workbook:
   • Press Shift+F11 to add a filler worksheet.
   • Select the first sheet, hold Shift, and select the last sheet to group them.
   • Right-select the grouped sheets and choose Move or copy.
   • In To Book, select (New Book), then select OK.
10. Try saving the file as a different format using File > Save As, such as .xlsx or .xlsm instead of .xls.
11. Update Office to the latest build: in an Office app, go to File > Account > Update Options > Update Now. A known issue with large Office files and OneDrive Files On-Demand was fixed in later Office updates.

If the Save and Save As buttons are greyed out specifically for files stored in OneDrive after moving from a Microsoft 365 setup, saving a local copy on the Mac is the most relevant next step.

References:

• Troubleshoot why Excel doesn't save changes
• Office files may not save if Files On-Demand is enabled
• Home Office 2024 cannot save Excel workbooks or updates to existing workbooks - Microsoft Q&A
• I can't save my excel doc. The Save as is greyed out. - Microsoft Q&A