Phone showing encryption unsuccessful

[midhun]

Hi im using sony xperia m c1904 it is rooted since 2 years, but from yesterday it is showing 'encryption unsuccessful' i cant do factory reset and installation of new rom is not possible i have tried installing new kernel using fastboot but it is not replacing the existing kernel, i've even tried installing new firmwae using flashmode but getting error if anyone can solve this prob it will be a great help for me.
hoping solution