Yeah, I was also thinking it might not be loading your project, and that does seem to be the case.
I tried this myself locally and as long as the .uproject is the first argument, it should be treated as a project rather than a map.
Is your project definitely built for the correct editor config? Bear in mind that without “-debug” on the commandline, it’ll be trying to load the “Development Editor” rather than “Debug Editor”/“DebugGame Editor” build of your game.
Also, just to rule out any bat weirdness, does the same thing happen if you run that command directly in cmd?