How to fix play store signing in issue?
have you tried backing up the files you would like to keep from the device onto the SD card, and reflashing a fresh system and GApps .zip entirely? this may solve your issue, but i am unfamiliar with the common operation of your specific device, this is sort of a blanket, last resort panacea type solution. hope this helps :] Note that this requires a decent fastboot usage knowledge and root access