Give BA a call and chase it up. If they already have a copy of your MH boarding pass, thus proof that you'd hit 1500TP, you could ask if they would put a note in the booking asking for entry to the F lounge? Otherwise just wait it out and hope it posts. The system will take 3-4 days to update to Gold though, even once the TPS have posted.
Was your MH flight definitely giving you enough TPs to get you Gold? Double check before you call.