Kobruk
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You could try simply downloading and extracting it again.
I also thought that might be the problem. I've downloaded it several times and even tried an older version of the mod and an older patcher - the error was definitely there, but I didn't check if it recognizes the maps...
Even if you run it with administrator privileges, the result doesn't change; it doesn't recognize the map. If you create a larger (X) map, the error is also present, but it disappears on the second attempt, and then the map is recognized.
P.S. I place the maps in the following path: D:\Games\HoMM_V\HOMM_V_ToE\Maps