Try opening your 2019 return on the Mac. Do you still have the program installed? Launch it and see if it opens your return. Go up to File-Open. Your tax file ends in .tax2019 and should be in your Documents. Then save it again do you can find it.
How to find tax files on Mac
https://ttlc.intuit.com/questions/1901659-find-your-tax-data-file-in-mac
