Hi,
something is up, because I have similiar problem...
since I installed the newest version of Addon Manager and Vehicle Update I also have problem with GSX sounds.
First FSX' run after install the newest Addon Manager and Vehicle Update I get Couatl Error - unfortunatelly I didn't do screenshot. After close error message, FSX run normally, but without GSX in Addons menu.
I opened Settings dialog and saw that no audio device is set and there aren't any audio devices on the list to choose - it's strange.
So I ticked "Restart Couatl and repeat audio diagnostics checks" checkbox and after Couatl restart had an error like this:
I shut down FSX then fire it up again and next Couatl error appeared while FSX was starting - unfortunatelly don't have screenshot.
I closed this error message, FSX opened normally, but without GSX in Addons menu.
So I shut down FSX and run again - no Couatl error. But when I load the flight, next two errors appeared (one by one):
Then, the flight loaded normally, but without GSX of course.
Something is wrong that I don't see any audio device in Settings dialog but I don't know if all these errors are related with it.
What can I do to recognize a reason of problems and why there is no sound?
Ps. In log file I found following entry:
Initializing audio...
Detected failed previous attempt to enumerate audio devices: disabling audioLucas