I have a Sony Media Player on the front end of my preamp. Sometimes my router just decides not see it anymore and it will not show in JRiver. And, all the while, JRiver and router are seeing the TV and Marantz TV amp but not the Sony. My hack is to turn the router off and back on. Then it sees it again and JRiver can pick it up.
I tried turning the Sony on and off, disconnecting it from the router and then reconnecting, rebooting the computer, reconfiguring the wifi connection between the Sony and the router. None of those worked to get it to show in JRiver even though when I reconnected the Sony to the wifi it said it was connected with no issues. But, turning the router off and then back on does the trick. So, I have no explanation for what is actually happening but just know how to fix it.
BTW - I never had this problem with the previous AT&T router. I changed to NorthlandCable and now have this happen about once every three weeks. It is aggravating but at least the fix is pretty easy.