Don't hold onto the idea that it's a complete loss. Everything should be in English, no Russian letters, I've read the entire forum. The problem is specifically with the maps that I create from scratch; they don't appear in the game (they are present in the maps folder, and the file name is in Latin characters).
P.S. My friend has the same problem; he does everything correctly, but the maps don't appear. Today, I'm going to solve this problem at his place; if I find anything out, I'll let you know.
P.P.S. Maybe they are located in the network game, on the computer, not in the single-player game?
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Cr@zy Wolf is right. Your game path probably contains Russian letters. That's why nothing was appearing for my friend.