Do you have anything listed in Boxes 16 or 17?
You can only leave Box 15 blank if Box 16 and Box 17 are also blank.
If you are encountering an error with your 1099-INT, first delete the existing form and then create a new 1099-INT, following all the original entry steps carefully. Should you continue to receive the same error, try an alternative solution by entering only the two-letter state abbreviation in Box 15 before proceeding to the next step.
Just in case, here's a breakdown of the steps from this article on how to enter them:
Form 1099-INT reports interest from banks, brokerages, and other financial institutions. Choose your product for info on how to enter a 1099-INT.
I had an issue with an imported 1099-INT (from ALLY) where the imported put a bunch of 0.00 values in various boxes.....particularly box 17 for state.
The software had a particular issue with the 0.00 in box 17, and making that box blank fixed it ....but I went ahead and deleted all the other 0.00 values too, to avoid any other possible issues.