1. Do you have custom recovery (CWM/TWRP, etc.) installed? Then you can’t install the update if you have it. You need to flash the stock recovery via ADB to fix the error.
  2. Have you deleted a system app from your phone? Or have apps like Xposed Framework installed? Then you should get back the system app to /system/app folder and uninstall Xposed Framework.
  3. If nothing is installed or modified your device, but still receiving the status 7 error, try factory resetting your phone and install the update. It should solve your issue.