[CentOS] Mate and USB headphones

Logitech H540 headphones were working fine.

Suddenly stopped.

Sound Preferences says they are disabled but gives no hints on how to enable them, or how they became disabled.

Tried rebooting, unplugging them, etc.

Anyone know what is going on?

This motherboard doesn't have onboard sound, this USB is my only option. And GNOME simply isn't usable for me, I used GNOME for years but GNOME 3 literally gets in my way all the freaking time trying to force me to do things the new way that just aren't conductive to my thinking style - so MATE is what I use.

I have no clue how these headphones became "disabled" or how to change them back to enabled.