N910t 5.1.1 bypass msl security error

Objective : Write a new cert

Problem: Im running 5.1.1 on n910t…. I keep getting error when trying to reset msl… I have tried downgrading the modem to nk4 then resetting msl but I get the same error…The port and everything else is detecting fine..I also tried downgrading firmware but I cannot downgrade firmware to 4.4.4 because it gets error on odin… Anybody know how to solve?

Thnks in advance!