FQHC would have it's own billing requirements and regs. You would always need to refer to the manual specifically for FQHC. If you look at the denial reason on the claim, it most likely would have your answer.
170 - Mental Health Visits
Medication management, or
a psychotherapy “add on” service, is not a separately billable service in an RHC or FQHC and is included in the payment of an RHC or FQHC medical visit. For example, when a medically-necessary medical visit with an RHC or FQHC practitioner is furnished, and on the same day medication management or a psychotherapy add on service is also furnished by the same or a different RHC or FQHC practitioner, only one payment is made for the qualifying medical services reported with a medical revenue code. For FQHCs, an FQHC mental health payment code is not required for reporting medication management or a psychotherapy add on service furnished on the same day as a medical service.
From what the above snip from the manual says, it is included in the G0470 – FQHC visit, mental health, established patient. You can't try to bill two on the same day.
G0470 – FQHC visit, mental health, established patient:
HCPCS Qualifying Visits for G0470:
90791 Psych diagnostic evaluation, 90792 Psych diag eval w/med srvcs, 90832 Psytx pt &/family 30 minutes, 90834 Psytx pt &/family 45 minutes, 90837 Psytx pt &/family 60 minutes, 90839 Psytx crisis initial 60 min, 90845 Psychoanalysis