Missing app purchase on Mac
I purchased a desktop app back in 2017 and use it daily (Checkbook Pro). I recently got a new computer and want to transfer the app to the new machine. I cannot drag it or copy it over, so I was instructed to re-download it from the App Store- however, it does not show up in my purchase history. Back in 2017 I was using a different Apple ID, but the same account. Many other apps I purchased before changing my Apple ID do show up in my purchase history, but not this one. I can no longer sign in with the old Apple ID, so what do I do?
Mac mini, macOS 11.6