OK, here's the procedure:
1. Get the NICS transaction number (NTN) from the FFL, and any OH state number if they are involved.
2. Either email or fax NICS (be sure to specify the NTN), asking why you were denied. You should have an answer within a week. The FFL should have both the fax and email address to use. Do NOT waste time calling, they will tell you ZERO over the phone.
3. The reason you get will only state one or more of the federally prohibited criteria such as "you have been convicted of a felony" etc.
4. If you think they are wrong, follow their instructions, get fingerprinted and mail the information to NICS appeal section. If you think the problem is likely to occur again (mistaken identity say), consider submitting your appeal along with a Voluntary Appeal File, this way they know the story not just this time, but every time.
5. Wait 6 months or so for your certificate, go pick up your gun.
Good luck.