have been using 27.5 (perhaps incorrectly)
Yes, they have been doing it incorrectly. You do need to have that fixed too, as there is the possibility (However slim) that it could catch up to you in the future.
To fix it, requires you to include IRS Form 3115 with your tax return. While the TTX program does include that form, it's not simple by any stretch. You should seek professional help for this. Then, once it's "fixed" correctly on your 2021 return, you can if you like, start using the TTX program for your 2022 taxes.
