I know this post is really old, but I had the same problem now. I did everything and it dont works. Now I changed the partition from primary to logical. I dont know why, but it works now. this was the only thing that works.
Hey,
I searched for this topic for a while but couldnt find anything. I created a forwarder channel for USB Loader gx on the Wii U Menu. It can be started and it works, but when I start a game it brings me back to the Wii U Menu. Yesterday I did...