There is a lag between gaining EXP, and the updating of that fact in the OneWorld DB - I suspect one updates the other only once or twice a week (if that). I know this because I had the same problem in LHR recently - BA were refusing me access to the First lounge because I had no EXP card, and my status said Saphire on my BA BP. I get around this I had someone at the AA desk print a copy of my PNR from an upcoming flight, since that said Emerald, it sufficed for BA.

Since this is not possible at HKG, I suggest you print your account details page and just show them that. Good luck on the op-up.

KB