UPLOAD FAILED: We saved your changes but we couldn't upload them because the site is temporarily in read only-mode.

The message means Excel was able to save a local copy of changes, but it could not upload those changes back to the online location (SharePoint or OneDrive) because the site is currently in a read-only state or under maintenance.

When a SharePoint or OneDrive site is locked as read-only (for example, during maintenance or because an admin has set a lock state), files on that site cannot be updated. Office apps then show an “Upload failed” / “site is temporarily in read-only mode” message: your edits are safe on the device, but the online version cannot be updated until the site is writable again.

To proceed:

1. Keep the local copy that Excel saved so no work is lost.
2. When the site is writable again, reopen the file and let Excel upload/sync changes, or manually upload/replace the file if needed.
3. If this is a SharePoint/OneDrive for work or school site, an admin may need to remove the read-only lock or complete maintenance before uploads will succeed.

If the file was deleted or moved while editing, it may also be necessary to save a copy and, if needed, restore the original from the recycle bin.

References:

• SharePoint or OneDrive read-only error messages
• I got an "Upload failed" or "Couldn't save automatically" error while editing an Office file