I noticed the volume mixer was initially at zero % on my end as well. I manually raised the level of the slider and it's stayed at 100% on the slider even after shutting off and rebooting my PC, but even though it stays at 100% the game still refuses to output any sound. The game worked fine without issue for about 40 + hours, then earlier (the first time I ever had a problem) my game froze / locked up after alt-tabbing while being grouped up for MUT squads - I restarted my computer since Madden wouldn't close and this is the issue I came back to when my computer rebooted...extremely frustrating
Updated info: I completely removed my current driver and installed the latest Realtek hd audio driver from my motherboards website....After the entire process I load up Madden, still no sound