What does it mean when it asks for the amount of tax imposed by another state?

I have income in 2 states for the year that have income tax, but neither is my residential state. The form states that the section should be left blank if I am a nonresident, but then keeps saying there is an issue with the form and I need to put a number in the box. I then added up all of the taxes I paid for the other state and put it in the box but it kicked it back as well. Any information would be greatly appreciated.