TurboTax Won't Accept Form 1098 Box 2 of 0.00

That might be because the entry of $0.00 is wrong. Box 2 is supposed to have your outstanding mortgage principle on Jan 1 of the tax year. So if you have an amount greater than zero in box 1, there's no way the amount in box 2 can be zero. You may need to contact the lender/issuer for a correction on that.

Well, the account is a HELOC (Home Equity Line of Credit) that has been open for a couple years and had a balance of $0.00 at the start of 2021. I drew on the line during the year so I paid interest on that draw.

Enter a value.

Enter the amount of the first withdrawal you took in 2021.

OR

Enter $100. to make TurboTax happy.

That's a reasonable workaround, and it does work. I still think TurboTax should accept a legitimate value for the form.