How long did the dump take?
First things first. This may sound dumb, but make sure that the switch on your SD card is not in the lock position. Check that switch and make sure it is unlocked. If it already is we will move on to the next option.
Right after you click your mocha.elf file in your HBL, hold B in order to bring up the configuration screen. Your settings should look exactly like this
- Config view mode: expert
- Skip the menu on launch: on
- Show launch image: on
- Don't relaunch OS: off
- Launch System Menu: on
- redNAND: on
- SEEPROM redirection: on
- OTP redirection: on
- Use syshax.xml (coldboothax): off
If it looks like this hit A, then if it tries to dump the NAND again we need to check your partition. You will need to download the MiniTool Partition Wizard.
https://www.partitionwizard.com/
Open this program with your SD card in the PC and you should have a partition on there that says "unallocated" and it will be about the size of your Wii U internal memory. Post a screen shot of it if you can. Then we will go from there.
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Oh and btw it is normal for all the files to be erased on the SD card. When you press the power button to start the dumping process it formats your SD card first then injects a hidden partition on the drive, which is a copy of your sysNAND. This is called your redNAND, or "Redirected NAND" due to it being a clone.