My W2 has no Box d. What should I do?

What box from your W2 are you trying to enter?  Is it 12d?

It says the same as in Box b Employer identification number, then it asks for Box d Control Number. So, not box 12 d.

typo fixed

Some employers don't include control numbers, so skip that field.  You will still be able to e-file, but you may not be able to import your W2.  Select that you'll type it in yourself.