Did you use the Mac last year too? Did you use the CD/Download desktop program? You need to have last year's file ending in .tax2019 on your Mac to transfer into 2020. It should be in your Documents. But I think on my friend's Mac I had to use Finder to find it.
How to Transfer into the Mac Desktop program
https://ttlc.intuit.com/community/tax-data-file/help/how-do-i-transfer-last-year-s-return-into-the-t...
