For purposes of immigration PCC are valid for one year.
They applied last year, most likely had it done upfront, and this means the PCC are expired, due to AVOs lackadaisical attitude.
However, since the principal applicant has gone back to the USA, after he got his previous FBI report, he needs to get a new one, the old one is invalid.
They need to apply for a new FBI report, get the Nigerian one done.
However, being in the USA, it's actually illegal to send passports from there to AVO, a mail needs to be sent to AVO, stating the new residence of the principal applicant, they would ask for details of his status in the states, to confirm if he's going to get his passport stamped over there.
In the interim, let them send the email, medical can be done in the US , start the PCC application for both countries, and wait for their response, on where to send the required documents.
HOWEVER, if they find it convenient to get back to Nigeria ASAP, it can still be tackled within 15 days, they would send all they asked for, including proof that the FBI REPORT has been requested for.
The application would be on hold, pending when the FBI report is gotten.