You had ABP interest adjustment (Schedule B), and that's just one of the reasons the IRS requires you to file Form 1040

"ABP" is an amortized bond premium. This occurs when you purchase a bond at a certain price above par. For example, you paid  $1870 for an $1800 bond. 

Did you import your 1099-INTs or enter them manually? In either case, did you have an entry (even a $0) in Line 11 of either 1099-INT?

If you had a positive entry (>$0) on Line 11 of your 1099-INT, you will have an ABP interest adjustment. The TurboTax program will prompt you to upgrade if this adjustment cannot be calculated or reported using TurboTax Free Edition (Online).                          (Keep reading for more options!)

If you had a "$0" on Line 11 of your 1099-INT, you don't have an ABP interest adjustment, but the program thinks you do. You can try to manually delete the "0". If that doesn't work, you will have to delete the Form 1099 and re-enter it in the 1099-INT interview - any Lines with a "$0" amount should be left blank (i.e. don't type in a "0"). 

See our AnswerXchange article How do I delete forms in TurboTax Online?

Auto-importing my 1099-INT from Ally Bank resulted in a 0 being entered for Line 11. Deleting this entry and manually entering only the Line 1 information fixed this problem for me.

Online or Desktop version of TurboTax?

This error occurred while using the online web app in Chrome on my Windows PC.

Thanks. I tweaked the answer based on your experience.