Yu_Gi_Oh, Was it one ticket all the way through with both carriers on it, or two tickets but in the same booking (PNR)? If it was one ticket all the way through Virgin would (should) have given you boarding passes for both flights at Heathrow; I assume that it was one ticket all the way through as VS and HX have through fares that are cheap.
If two tickets you may have had to get the HKG-PEK boarding pass from HX, either online or at HKG (transfer desk). However if when you you tried to get the boarding pass for the HX flight the Virgin ticket LHR-HKG was still showing as OPEN rather than CKIN or USED then HX may have had trouble issuing the boarding pass. The online system could fail, but the transfer desk should have no trouble doing that at all.
If others were crying that sounds like it was HX screwing up somewhere, regardless of it being one ticket or two.
However your agent should be taking this up for you with HX. Are they a physical agency or an online one? The problem that they will have, aside from the Corona-clusterfuck, is that the new tickets you bought have now been used. Airlines have big problems refunding tickets that have been used, so at best they will try to offer a refund on the unused original ticket, which I assume was bought in advance at a cheaper rate that what you had to pay on the day..?