If you will clear all of your cache folders and restart your computer it will allow TurboTax 2021 to fully open and let you update the software and then you will be able to use the software. I had the same issue and got no support from Turbotax, so I called Apple and they had me create a new user with admin rights and then try to run the application and it opened and worked perfectly, so they then had me delete all my cache files on my original user login and it worked fine.
