I'm having the same problem...
I bought my StudioLive 16.4.2 about 10 years ago; it was worked flawlessly with every version of the Mac Os - INCLDUING Big Sur - up util yesterday, when a mac software update "broke" a lot of plugins and software. Everything has been reinstalled or repaired, so it all works - Except my computer no longer recognizes the StudioLive mixer. Since it's my main studio interface, this is a real problem...!
Hopefully someone will be able to solve this for us!