Be sure your two letter state abbreviation code is in place and then you can add a zero in front if the state ID number is five numbers or less. Be sure you do not use any dashes or symbols in this field.
The entry in box 15 state employer ID on your W-2 should not cause a problem with your return processing at the IRS or the state revenue office. If there are no entries in 17, you may leave the entire box 15 and 16 blank, as well. If you do have entries in box 17, please see an additional workaround below.
If the error persists , try deleting the form and reentering it. If you have "copied and pasted" to enter some of the information, it might have spaces or other invisible formatting characters that are causing the errors. Please be sure there are no extra spaces before the entries or after the entries. If you have imported into TurboTax, perhaps some of the data was damaged in the transfer and is not working properly, even if it looks correct on the page. Deleting the W-2 and manually entering it should solve the problem.