Have 2 w-2’s from the same employer one is complete while the other is reporting on lines 15&16. I’m trying to add the second w2 in turbo tax but not allowed to?

You are supposed to enter any extra state amounts from that employer on the one main W-2 that was issued.   Occasionally, W-2 forms are issued by employers in a way in which they can't put multiple state entries on the main W-2 form...but the multiple states they report  for boxes 15,16,17 go into separate lines on the ONE W-2 in the software.....not on two separate W-2 forms.

Separate W-2 forms are only used for multiple employers....( and on occasion, it can happen for the same employer if the company was merged or bought out by another company....but then the main boxes 1-to-6 would be broken out separately into before-after merger amounts too)

Living in WI and working in MN.....

Hmmmm....it could also just be an extra state form for you to use IF you decide to paper file in WI, or MN, or both.   When you paper file a state tax return, you have to send in State copies of the W-2 forms....so the employer can't know if you will be paper-filing in both MN and WI, so they would provide extra state copies so you could paper file in both states...should you choose to do so, or if you are forced to do so for some reason.

In the TTX software , it would still only be one main W-2 that you would enter.

To add another state on the W-2 for boxes 15, 16 and 17 click on +Add another state