Moto G (XT1033) Official Update iNSTALL ERROR

I am using XT1033 model (INDIA), I got the Update notification today so before downloading it i made sure that i unroot my device (MY PHONE IS ROOTED AND BOOTLOADER's UNLOCKED), I did the unrooting process using the inbuilt function of SuperSU app. After that i rebooted the device the superSu was gone i checked the root status with root checker which confirmed my device was NOT ROOTED ,. After that i started the OS update it downloaded the 208 MB file then as usual started the installation and in the middle of this process the boot animation popped up and my phone rebooted and flashed the message "THE UPDATE INSTALLATION WAS UNSUCCESSFUL". PLEASE GUIDE ME THROUGH THE PROCEDURE OF INSTALLING THE OFFICIAL OTA UPDATE 5.1.1.