Well, now I'm baffled. I see the IP address of the TV is in the same address range, so there's likely no issues there. I'm at a loss.
Are there any other devices on your network that your TV is seeing, perhaps a Windows 7/8/10 PC with media sharing enabled? I'm looking to see if the TV is seeing anything else on your network. Just trying to eliminate possibilities.
Is your TV hard wired, or using wireless? Some wireless routers allow devices to connect but block access to other devices on the network. If it's there it should be able to be turned off. I realize it was working before, I'm just reaching.
I just did a quick web search for your Server and UPnP, and it mentions that Network Discovery needs to be enabled for UPnP to work. You can check that as well. My home server is running Home Server 2011, and when I tested Serviio on it it was fine. I suppose it's possible that Microsoft removed some UPnP functionality from Server 2016 for security reasons, but I wouldn't give up yet. But it's tough to troubleshoot when I can't see the screen or touch the keyboard!
EDIT: one more question. Can anything else on your network see Serviio on the server? Another computer running VLC, or a cell phone with a DLNA app? This would confirm if the problem is the server or the TV.
Dan
LG NANO85 4K TV, Samsung JU7100 4K TV, Sony BDP-S3500, Sharp 4K Roku TV, Insignia Roku TV, Roku Ultra, Premiere and Stick, Nvidia Shield, Yamaha RX-V583 AVR.
Primary server: Intel i5-6400, 16 gig ram, Windows 10 Pro, 22 TB hard drive space | Test server Windows 10 Pro, AMD Phenom II X4 965, 8 gig ram
HOWTO: Enable debug logging HOWTO: Identify media file contents