Today, for the very first time i got this problem. I did a DSIwareHax systransfer. I did downgrade NFIRM everything OK! 0 ERROR. Tried to downgrade and Can't get AM:U Service!!! something like that. So i opened 3DSident. And nFirm was 2.52 Tried again and again to Downgrade NFIRM. But didnt works. So What happen!! 1. When i tried to run nfirm downgrade first time after systransfer, the screen goes black, and return to power of console option. 2. Before run nfirm downgrade i did a FULL NAND backup 3. I restored the FULL NAND backup and tried again and this time works. nfirm 2.50 Something was wrong due to nfirm downgrade, a NAND restore solved the problem. So it's alot of important to do FULL NAND backup before do anything. Use https://github.com/Plailect/dgTool/releases/tag/v2.0.0 And DUMP NAND before start nfirm Downgrade!!