My Wii U is on 5.5.1
I downloaded this elf so it must be the latest version. It was uploaded 1 day ago. https://github.com/BullyWiiPlaza/tcpgecko/blob/master/tcpgecko.elf
I started a new game at the beginning and enabled the infinite stamina code to see if the code worked but it didn't. I don't have java on my PC as required by the Gecko-U-Updater. I manually downloaded TCP Gecko at the link earlier in this post.
Odd. If you want to install Java and JGeckoU, I'll take a look at your memory dump.