I was having this exact issue and I was able to fix it by copying the CNCMaps.Shared.dll from an old (8-12-2015) install into my new install.
I have windows 10, which includes .net 4, so I don't think .net is the problem.
I think it's missing that file which is the problem.
Now my maps are all rendering! It's taking a few minutes, but hey - I can see them and see the start spots.
Also, when rendering the maps, if you click on the map that's currently rendering, it crashes the game. Best to wait 10-15 minutes for them all to render.