On OSX. Euro N3DS Downgrading from 10.3 I needed to do this:
https://www.reddit.com/r/3dshacks/comments/3zrnah/to_all_mac_users_trying_to_downgrade_that_get_a/
Essentially use BlueHarvest to get rid of all the hidden OSX gunk and then it worked straight away :)
I get the same error message titleException:, main.cpp:140; Result: 0xD8E08067, Failed to get CIA info message.
At least this time it is the furthest I have got :)
Tried this:
Via Ironhax entry point it Sysupdater froze at stage 5. Repeatedly.
Tried via Menuhax.
Got as far as Press Y to downgrade. Pressed Y. Nothing happened. Waited a long time. Nothing happened. Eventually powered off and on. 3DS still working but not downgraded.
Think I will wait for...