I am also having this issue. As people have figured out, it's triggered by having refinanced my home loan in 2020. There needs to be a fix or official workaround to this. I'm using the online version and can't figure out any way to fix it.
Editing to add that the work around I used was to set the principal balance of the loan I took out this year to $0. That doesn't comply with TurboTax's instructions, but it makes logical sense as what matters for all other loans is the balance on Jan. 1, 2020. As long as you're not near the $750k limit for principal, it really doesn't matter - all that goes on the actual tax return is the amount of interest you paid.
