Some Excel files may have the Shared Workbook feature enabled. This feature has ben replaced by co-authoring. Microsoft lists the limitations here:
About The Shared Workbook feature
When an Excel file with this legacy feature is shared via OneDrive/SharePoint, you may receive an error stating:
“We couldn’t open this workbook because this is a shared workbook.”
You can also tell if the Excel file has the Shared Workbook feature enabled if - Shared is next to the file name.
Disabling the Shared Workbook Feature
1. Open the Excel file in the Desktop App.
2. We first have to find the Shared Workbook button. Select File, then Options.
3. Select Quick Access Toolbar.
4. Under Choose commands from, select All Commands.
5. In the left side column, scroll down until you find Shared Workbook (Legacy). The list is alphabetical.
6. Select Share Workbook (Legacy) and then Add >>
This will move Share Workbook (Legacy) to the right column. Press OK.
7. Select the Shared Workbook icon at the top left. This will open the Shared Workbook Options.
8. Uncheck the option to used shared workbooks. Then press OK.