It is saying I need to enter Emplyer's state ID number but it is blank. It keeps popping up as an error. What can I do? I do live in one state and work in another.

1) IF...if the employer's state is a state with no income tax, you leave boxes 15,16,17 entirely empty.

2) If there are $$ in box 17, then there must be an employers ID in the second part of box 15 and you'd need to get that from your employer.  Don't put a zero in box 17 if it's empty, leave it blank.