Should my non-MA source income on Form 1-NR/PY be something other than the other state's box 16?

TurboTax won't let me file because it insists that there is an error on Form1-NR/PY: Non-MA source income.  I am a part-year resident, no longer residing in MA.  I put in the value of box 16 for Maryland, my other state.  It rejected it.  It also rejected 0. It also rejected the value from box 1.