It sounds like this is asking for the Utah withholding ID, which would vary based on the issuer of the 1099-K. If you don't have any state tax withholding (which is most likely the case) leave all of the state income boxes blank including the "UT" in the dropdown box. This should resolve any error related to a missing tax ID number.
If you do have withholding, you'll need to get the number from the company that issued the 1099-K to you.