The document was saved successfully, but Excel cannot re-open it because of a sharing violation. Please close the document and try to open it again

Make a backup of the file
Open the file
Click on ‘File‘ and ‘Inspect Workbook
In my case it found ‘Custom XML Data’
If you don’t know where this comes from and what it does, remove it
Save it – should work normally now

https://answers.microsoft.com/en-us/msoffice/forum/all/the-document-was-saved-successfully-but-excel/edb4f192-546b-4fa9-8c04-42e3f631046b