I have the same Issue, but i am actually on GPortal. Any Chance you already know the solution? ^^
Just in case:
Version: v1.12.7 (Stable)03/10/2020 14:09:43: Critical error occurred
System.NotSupportedException: This protocol version is not supported.
at System.Net.Sockets.Socket.set_DualMode (System.Boolean value) [0x00014] in <4bf78e13a6ea4494a3898e6a836a77f4>:0
at Vintagestory.Server.ServerNetManager.StartServer (System.Int32 port, System.String ipAddress) [0x00030] in <85df978245df42d0bcb8a0dc9a428df2>:0
at Vintagestory.Server.TcpNetServer.Start () [0x00000] in <85df978245df42d0bcb8a0dc9a428df2>:0
at Vintagestory.Server.ServerMain.AfterSaveGameLoaded () [0x000f7] in <85df978245df42d0bcb8a0dc9a428df2>:0
at Vintagestory.Server.ServerMain.Launch () [0x00207] in <85df978245df42d0bcb8a0dc9a428df2>:0
at . () [0x000b8] in <50f7fb12b6b440cc83312c0d37e3a1f8>:0
at _a4XSOisFTJ6s4VNuUhZB7PjdJMH._tPBoCn18xTTokcQIGDykhW5AvOD (System.Threading.ThreadStart ) [0x00007] in <85df978245df42d0bcb8a0dc9a428df2>:0