It is likely that there are too many digits for that field entry. If
your state employer ID number is too long (too many digits, that is) to
fit in the field, then just enter as many as you can in the box, and
as space allows. Your e-file return will still go through just fine, as
long as there are no other errors on your return. Your state
department of revenue will be able to easily identify your employer from
their 9-digit federal EIN.
The state employer ID number is
really only a bureaucratic convenience for your state's department of
revenue; it's simply not an essential element to the correct filing and
processing of a valid personal income tax return (either state or
federal). Try to input it correctly if you can; but if you cannot, then
it's not a problem. You can also omit any dashes and spaces.