I used to have a Meridian MD600 and 218 Controller connected to my Mac via powerline. Everything was ok until the internet provider changed my router for a new one.
Since then I can not see the 218 in Roon, but I continue seeing it and playing music using the Soolos web browser (ControlMac is not longer supported).
Router + Powerline + Switch + connexions to 218, MD600 and 861.V6. Everything working fine.
The distance between my Router and Meridian equipment is about 10 meters.
If I bring the 218 close to the router, even with the switch in between, I can’t connect it to the Meridian equipment, so I can’t test.
I mean, just connect it to the router and see if you can see it in Roon. If you can, it may point towards the power line. Have you re booted your power lines? Always worth a go.