I reported a similar issue about two years ago, now the issue has come back: Roon does not show my Linn DS any more as a zone when the PC wakes from sleep. The Linn still shows up under Airplay devices but the Roon specific Linn connection is gone. Once I quit and restart the Roon server app the Linn shows up again with the queue in the state it was before it disappeared. Unplugging and replugging the Ethernet cable from the Linn or switching the Linn off and then on again does not resolve the issue. Only restarting the Roon server app solves it. I ran some additional checks with other control points (Linn Kazoo, JRiver) on the PC running the core. When I leave either of these control points running when I put the PC to sleep, they remain connected and the Linn shows ready to play immediately on wake of the PC. The same goes for the controllers on my mobile devices.
My core is on a PC running Windows 10 V 1909 build 18363.836. Roon core and remote are V1.7 build 537. The Klimax DS is running software version 4.75.360. Both PC and Linn use static IP addresses. My router is a Unifi USG Pro 4. Both the Linn and the PC running the core are connected to a Unifi Switch 8 via Ethernet. Switch configuration is as recommended in the Roon network best practice. @Support can you please look into this and let me know how to get this back to normal.
P.S.: all my Sonos devices remain connected to the Roon core and work fine immediately after PC wake from sleep.