I'm a ND resident, work part time in MN. Each year I complete and file an MWR for withholding at my MN job. Why did I have to file MN state taxes?

[SteamTrain]

IF you filled out the MWR for 2019, and IF no MN income and no MN taxes were withheld   (boxes 15-to-17 on the W-2 form)

THEN you DO NOT indicate you worked in MN in 2019 in the "My Info" section of the software.....the job there is then treated as if it was all done in ND. 

The only time you need MN, is if the W-2 shows MN wages or MN withholding....and the you'd have to file non-resident MN, with zero income indicated, to get all the MN withholding back.

IF no MN income and no MN withholding on the W-2, then Fix the My Info page to take MN out as an other state you worked in....then delete MN from the states section (should be a trashcan next to it IF you started one)