Figured it out. My WiFi connection had somehow been flipped by Windows 10 from Public to Private.

Start with looking at the Firewall on the Windows PC and make sure it isn't blocking the MMW server.

Am I the only one who is experiencing this? MM 4.1.7.1764 and MMA 1.1.3.0499. Everything was working last week so it seems to be since the Windows 10 upgrade. I cannot sync or use the DLNA player as neither of my tablets can "see" the server.