We have seen this a couple times. I have ignored it but I now need to know what is causing it.
- This Excel document was being used by one person
- The person uses Sync to open the file
- This error occurred during an attempt to save this morning
- There are no revisions in the web app since yesterday at 3:42pm
- The file name has been removed from the image below
- This has happened as well to Word Docs