We have been using the Syrinscape online player for a couple of years now and no problems. Fantasy Grounds 4.4 comes along and suddenly none of the players can hear anything. We have tried just running Syrinscape alone using the online player (not web player) and we cannot get any sounds shared by me heard by them.
Other than the FG update we havent touched the Syrinscape installs. any ideas?
I think I have solved it - it seems to me that my M1 mac is the culprit. A recent OS update I think broke permissions. I disassociated and re associated the device and this seems to have done the trick.
Oo yay!
I wrote a whole response and then missed that you had actually got it working. 
Any reason you are NOT using the Web Player? It IS more straightforward for getting set up for everybody!