I am running Roon v1.8/build 831 (latest version according to the settings info in the app)
My platform is MacOS Catalina 10.15.7 my DAC is a Pro-Ject Pre Box S2 (via USB), and Yamaha Amplifier S501
I’ve been using my Pre Box S2 Digital DAC for 3 years, but suddenly ROON stopped showing it, I don’t have the problem with other apps (Audirvana, Tidal, Qobuz), which recognize my DAC perfectly, not even iMac output shows
Have you tried the usual stuff….
power down dac, then roon core then the router, power up in reverse order. Devices usually disappear when network related problems occur, the process mentioned usually sorts it out (sometimes you might have to follow the process a couple of times).
Also, if you’ve followed the link on how to report errors in your other thread about this problem, you could upload a set of logs for support to analyze - that would likely speed up the process of getting to grips with your situation.