There is no sound from the 7.1 surround sound system

When I open the 7.1 audio app, the sound cuts out completely. I’ve tried every possible combination of audio device selections. Since 7.1 surround sound wasn’t working, I downloaded THX to see if I’d experience the same issue there, and 7.1 works flawlessly within THX. When I select any device other than 7.1 surround, it displays an exclamation mark; when I select 7.1 surround, it appears to be working but no sound comes through at all. I’ve checked all my updates, including Windows and the 7.1 driver, and everything looks normal. It used to work before—I hadn’t used it for a long time, and when I tried to use it again, I ran into this problem. I haven’t used any other audio apps during this time. I don’t know what to do. I think there's a software conflict caused by the updates that were made