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When I start the game I still have sound and sfx, but as soon as the match starts everything goes silent. When I go back to the main menu the sound doesn't come back either.

I tried running on compatibility mode service pack 2 and 3 but it didn't solve it. Weirdly enough, right after the WBC3 installer finished and I launched the game through it, I had sound in game. After starting it a second time it was borked though.

Windows 10 64bit
That Happens to me too from time to time.

One solution is go to the options sound menu and click on Full Effect for sound...For some reason it seems to reset to off from time to time.

Be sure to save your game before you quiT
Hope that helps