I am unable to host/join any maps other than melee maps. This includes the “_LV” melee maps that appear in my Downloads folder. At creation/joining I am sent to the map lobby with all character slots blank and no controls/chat function. I have tried deleting the Maps folder, reinstalling the game and moving custom maps outside the Download folder (they appeared in the list with melee maps) to no avail.
Check cloud backup solutions like one drive, perhaps disabling them. Otherwise maybe your Windows user account name is breaking the file system logic due to non-ASCII characters, something one would assume fixed but maybe is not fully given that Warcraft III was not Unicode aware originally.