Did you follow this below, if not you may have bricked it. Hard mod only to recover, if so.
"Validation Stage 1: FAILED" and "Validation Stage 2: FAILED"
THIS APPLIES ONLY TO .TMD RELATED ERRORS, NOT .APP RELATED ERRORS
If you got a .app related error, you should restore SysNAND from sysNAND_original.bin, restore RedNAND from emuNAND_formatted.bin and retry from Part 4 - Section II - Step 9..
- Check otphelper.log to see which titles the TMD hash mismatches on
- Download the latest release of GodMode9
- Copy the GodMode9 folder from the GodMode9 zip to the /3ds/ folder on the root of your SD card
- Get into the Homebrew Launcher on SysNAND through the entrypoint of your choice
- Open GodMode9 (Be VERY careful with this tool, it can brick you if you delete something important with it)
- Select (on bottom screen) emuNAND CTRNAND
- Select title
- Select the folder which has the same 8 characters as the beginning of the title that mismatched (for example, if you mismatched after Checking title 0004013000003202... then you would select the 00040130 folder)
- Select the folder which has the same 8 characters as the end of the title that mismatched (for example, if you mismatched after Checking title 0004013000003202... then you would select the 00003202 folder)
- Select content
The latest release of OTPHelper rarely shows false positives, but if you want to you can check manually just to be sure. To do this, press A on each .tmd and select "Calculate SHA-256" to manually compare to see if at least one of the .tmd files in each folder match a Sha256Sum to
this list.
If, in each folder, at least one of the .tmd files matches a hash on the list, this was a a false positive and you can use the following steps. If it is a New 3DS you should unbrick EmuNAND first. Go to "NAND Backup & Restore" -> "Clone RedNAND to SysNAND" then use "NAND Validation Options" -> "Validate SysNAND Downgrade" and confirm your SysNAND only has the same error as EmuNAND. If you get a NEW error after cloning RedNAND to SysNAND, restore SysNAND from SysNAND_original.bin, restore RedNAND from emuNAND_formatted.binand retry from Part 4 - Section II - Step 9. If you do not get a NEW error, continue with the guide, ignoring the error.
If, in any folder, none of the .tmd files match, then this was a legitimate downgrade error and you have been saved from a brick; you should restore SysNAND from sysNAND_original.bin, restore RedNAND from emuNAND_formatted.bin and retry from Part 4 - Section II - Step 9.
Check all of the titles that mismatch with this same method.