G531f imei null how to rapair

AFTER FLASH IMEI NULL 3 TIME CHANG FIRMWARE BUT SEM PROBLEM WRITE CERT FILES BUT SEM PROBLEM THIS HWK PROBLEM / SOFT POSIBLE?

Platform: Samsung Android
Selected port: COM268
Selected model: SM-G531F
ADB server killed.
Please, press "OK" button on the phone to allow USB debugging..
Please, press "OK" button on the phone to allow USB debugging..
Detected phone model: SM-G531F
Firmware compiled date: Tue Aug 4 19:58:27 KST 2015
PDA version: G531FXXU1AOH1
CSC version: Unknown
SW version: Unknown
Phone SN: R58G81PC0RM
Android version: 5.1.1 (LMY48B)
Cheking Root
Phone is Rooted
Preparing…
Writing Certificate…
Selected file: C:\Documents and Settings\sadiqsajan\My Documents
\Downloads\cert-sm-g531f_35230307313620.cert
Checking Certificate file…
Certificate file successfully checked
Finalizing…
Certificate has been written successfully
Please, restart the phone to apply changes