afaik, the new gproxy downloads the latest dota map for you, but im not sure. Anyways, check manually if your map is in the right folder, it should be Warcraft III/Maps/Download
(ofc your war3 folder name can be vary.)
Also check to be sure that your map name is the exact same as this: DotA v6.81c.w3x
If there are some (1) (2) or any other shits in the map name, it fails.