What Do I Put when the employer’s state Id number is missing

You ask the employer for a corrected W-2 that includes it.

@dionna_f  very much agreeing with @xmasbaby0  for a W-2. However, if it is a 1099-R  or even for W-2 sometimes  and for some states the Federal  (EIN) is also the State  ID. So if it blank  you possibly can get away with using the federal id  and see if that works -- I know this is true for MI at least

@pk     Good point---my brain just went to W-2---you are right about other documents!  Thank you!