Well this is the problem here.
If the system layout was mentioned earlier we could have spotted this and saved you a lot of time 
.
HQPlayer can play over the network but only to “NAA” endpoints.
Kind of like Roon playing to Roon Ready/Roon Bridge endpoints over the network.
Roon can see your Bridge II because the Bridge II network card supports Roon Ready. It does not support HQPlayer’s NAA protocol.
If you had a Raspberry Pi4 you could use that as HQPlayer endpoint (NAA).
So HQPlayer can play over the network but not directly to your Bridge II card.
Hope that makes sense? If not, just check what the Bridge II supports and you will not see HQPlayer NAA mentioned… it supports Roon, UPnP, Spotify Connect etc.
I assume your Roon Core and Bridge II DAC are not in the same room?
Apologies if I’ve guessed your system layout wrong here. Just trying to help