I'm trying to add a new payment to make a booking, and face the same problem as postcode.
There's no such thing as postcode in HK. I check the mail from my bank which issue the credit card, there's no postcode. I tried every combination suggested on Google (000, 0000, 00000, 00000000, HKG), nothing work....
The conclusion is - I really want to make a booking but I couldn't because Airbnb seems to understand there's no postcode for Hong Kong (while I never have a problem making payment online everywhere else with my visa) 😞