IOSUHax/CBHC/Haxchi/Mocha SD loader error codes list:
-1 : HBL related, can't open or not enough memory to open HBL elf file
-2 : HBL related, entry point not found
-3 : SD Card not found
-4 : SD card found, can't mount it
-5 : SD Card found, can mount it, can't find/read/open the file
-6 : not enough memory to open file
remember that all the apps need to be on the WiiU/apps not only apps,because thats for the Wii side
do you have a screenshot of the wiiu folder?