My FHR booking didn't credit for over a month. Then I chatted with an AmEx agent. He took a few minutes to check my booking, then stated that I met all the requirements, and that he'd issue a manual credit. It posted a week after that chat (backdated 3 days).
I noted that the hotel folks always referred to that booking as "prepaid", and never mentioned FHR or any extra benefits. I was fine with regular Diamond benefits, so had no incentive to investigate further .