I have the IDENTICAL problem. I’m on a MacBook Pro 2020 Intel chip, Big Sur 11.4. URC22C connected via hub, which has worked flawlessly for months. I’ve done NOTHING different. It is powered from the hub and the power is fully on and I can set my audio to go through it successfully.
I’ve gone through the Steinberg website and uninstalled/reinstalled all software and I still get NO DEVICE FOUND in dspMixFX. In the Audio Midi setup the symbol for the Steinberg is a BLUE USB symbol, neither the black found in the troubleshoot or the red it is supposed to be. I’ll paste a screenshot at the bottom. I’ve gone into security/privacy after reinstalling and there’s no option to allow privileges for this software. I did see in the e-license control center where it wants an activation code-when I first installed the product I entered the code, but now it wants it again and I don’t have it; however the problem began BEFORE I did the reinstall.
The ONLY thing that changed on my computer was that I just installed Google Drive desktop and I had to give permission via Security & Privacy for that product. I can’t tell you that dspMixFx was detecting the UR22C immediately before and now it has stopped, but I do know that as of yesterday it was detecting it. I got the “no device found” after the reboot from installing Google Drive Desktop.
Pasting screenshot of audio midi interface below, hope it works: