Please read "Maryland HomeCredit Program - Lender Information".
This program sounds like it is based on "Mortgage Credit Certificates ". These certificates are issued by the mortgage lender or by the state, based on how much money is available from the state for this program.
It's possible you had to apply already for an MCC to be eligible. Please contact your mortgage company and see what they know.
At the moment, I can't find the Maryland entry for this credit in TurboTax, but, then, again, I don't know if you are still eligible.