N910C bootloop after downgrading

I have n910C with bootloop,
The phone came to me to remove Samsung Reactivation Lock ,it was on 5.1.1 so I tried to downgrade it to 5.0.1 using miracle box( by unchecking sboot.bin and modem.bin) after that the phone still in bootloop case 🙁 .
I tried to downgrade it to 4.4.4 by the same method and it’s the same result .
How can I solve it please ?