You didn't mention what state.
If this is Utah, be sure that it is 14 characters and no hyphens. It should be 11 digits and then ending in wth (in lower case). Example 12345678911wth
It has to be that way on all your W-2's and 1099's that have a Utah state withholding ID.
If you already did that, and still getting an error, delete the W-2 (or 1099) and enter it from scratch. Again, be sure to use lower case for the wth