Hi
My name is Daniel. I am an Independent Advisor.
As first troubleshooting tips, to prevent unwanted issues please ask your colleague to make the backup files first. On the Excel desktop app, please select File > save as > select SharePoint > select team channel. (see screenshot)
Once the files have been successfully backed up then your colleague can cancel the dialog box.
As an alternative, your colleague can sync the Team files to the local computer by using the OneDrive app then co-edit from there
Step 1: Sync the Team files to the local computer.
The following article explains how to sync MS Team files via the OneDrive desktop app.
https://www.onmsft.com/how-to/how-to-best-sync-...
Step 2: (Optional) Un-sync Team files from their PC:
This is optional, If your colleague no longer needs to sync Team files to their computer then they can follow these steps below to un-sync files:
- Right-click the blue cloud icon at the taskbar > settings > account tab > choose folders > uncheck folders you don't need > click Ok
- Under the account tab > select unlink this PC > select unlink account
This is a peer-to-peer support forum. I'm Non-Microsoft Staff, I don't work for Microsoft. Mostly everyone here are users, helping other users.
DISCLAIMER:
There's a link above from the non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
Kind Regards