It’s been two separate items for years but last week they decided to merge it even though they have different UPCs.
It’s asking for the original ASIN and the current but I don’t know the old ASIN.
Is there a way to find it? Or is there another way to unmerge them?
That’s not a big deal You can solve it by Inventory file (flat file). Download inventory file from seller central and put all products details on it and after that again upload this file to seller central. Via doing this Amazon will automatically merge your desired items as you want.
Check your old emails and previous business reports to get your old ASIN.
I recently fixed same issue via flat file.