I'm having a problem, emunand downgrade is successful, but otphelper says validation failed ;-; I checked the SHA256 and it matched too.
I've had that same issue as well. Apparently OTPHelper can't detect multiple TMDs in the same folder so I did the rest of the guide and even though it froze to a black screen after I rebooted, I hard shutdown the system, pulled out my SD Card and then turned it on without it and low and behold it booted fine. So I reinserted the SD Card and continued the guide as normal and now I have A9LH on my o3DS