Have you ever tried this method to fix dstwo firmwarePosted by gamekool admin
I just got a method for fixing the firmware after upgrade dstwo firmware failed.
1. You need a DS/DSL and another flashcart which can run homebrew (e.g. r4i gold 3ds, ace3ds plus… etc)
2. Download the latest dstwo EOS and dstwoupdate.dat file which from the latest fireware of DSTWO.
3. Run dstwo_load_NDSL.nds and dstwo_load_NDSL.rar with another flashcart which can run homebrew (e.g. r4i gold 3ds, ace3ds plus… etc)
on a DS/DSL, then you will see this screen:
4. Insert DSTWO (without microsd card)
5. Insert the microsd card which stores latest EOS and dstwoupdate.dat file into DSTWO
6. Press B to continue.
Just have a try.