Has it ever worked at all to show the device, or has it suddenly stopped? Also what sort of router do you have (make/model)? Also do you get the same issue on all PCs on your network (presuming you have more than one)?
One thing it might be is if your router is older or just slow, and when your network is busy then there is not sufficient speed for it to register the device. The simple way to check that is to plug your MC directly into your machine (plug the ethernet cable from it directly into your machine’s ethernet port) and see if the device then shows up under Quickview. If it does then your network speed may not be enough, and if it doesn’t still then it’s more likely a set-up issue with Quickview.
I had something similar with my old router - my MyCloud Mirror did show under QV but some of its right-click options were not available. Updating my old router to a new and faster one resolved it immediately.