Merge and Compare Error? "That workbook cannot be merged because it contains changes...."

[frogrump]

Error received - "That workbook cannot be merged because it contains changes that have not been merged followed by later changes that have already been merged into the current workbook"


Please help


The rundown:
I created a master workbook in Excel. I used "save as" to create a few copies of master. These were all saved in a shared OneDrive folder. Users updated their own copies. I used 'compare and merge', chose the first person's - it merged successfully and updated my master. I tried another, and another, and another, and the rest of these will not merge and give me the error above. Why? What can I do to fix this? How can I get these workbooks merged now that users have already updated their copies? I can't ask them to redo all that work
Thank you!

 

[frogrump]

I am super sad that I have searched about this error for 24 hours now....I've found people asking about this error 10 years ago, and nobody got a reply. What is happening? How can I save these workbooks and get them merged? Isn't there like a master Excel handbook which lists all errors and their resolution??