Amend 2020 Return -- TurboTax CD Premier not working?

Filed 1040SR using TurboTax Premier CD and the return was accepted and refund received. Just received a 'revised' 1099-DIV so need to amend the return. I waited until after 03/25/21 for when the 1040x stuff is supposed to be available and followed the instructions [ here https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-return/01/27439#sh-details_without... ]; but the TurboTax application seems to be broken. 

 

When I select "Amend a Filed Return" I am never given the option to open an existing return; it just starts a new return. Is this unique to the Mac release, since the TurboTax Online webpage makes it sound like it is supposed to work. My software is up to date.