Tiamat 7.1 v2 sound controller does not work. (No sound)

As the subject states, starting with Tiamat 7.1v2, at some point the sound stopped coming out.

When I select each channel with the selector, the indicator light comes on full blast after about 5 seconds, but no sound comes out no matter how much I turn the volume controller.

The mic mute and 7.1ch buttons do not respond when pressed, only the audio mute button does.

Is there anything I should check or has anyone solved the problem?

Synapse is up to date with v2.21.