i had this problem in the Alpha as well,i have sound in the menu,the cutscenes or when i discover monuments but no SFX or dialoge,music etc. in the vip beta everything was fine.
I tried to switch from home cinema to tv speakers then to headphones in the audio,resterted the game several time and nothing helped.
My sistem:
i7 8700k
Asus Maximus X Z370
16gb Gskill DDR4
Asus ROG Stric RTX 2060
Audio output-
Logitech Stereo speakers
Display Audio Speakers
Asus Strix V2.0
The private beta seemed better for me. Never had an issue solo. About 1/3 of my group play was completely silent, though.
Now, all solo so far, my gunfire drops out almost every encounter. Sometimes all sounds are gone. Once, the only sound was bullet impacts on enemies.
Then, a couple minutes later, I'll have 2-3 straight minutes of full auto gunfire. Strangely, it seems to change based on the weapon I'm currently holding (ie not really the audio "catching up" from a previous encounter).
This is definitely my biggest complaint so far. I'm getting some hit detection issues, too (crosshair red, but doesn't connect), but that could just be me thrown off from the poor audio.
Xbox One, open world and missions