So we can better assist you, please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so we can have a clear understanding of how your devices are communicating.
The next time this happens (your Bridge is running, your DAC is connected and powered on, but Roon doesn’t see it) can you please use the directions found here and send us over a set of logs using a shared Dropbox link (or any other file sharing service)? Thanks!