Update Notification Not Appearing: Ensure the file name has not been changed. It must remain exactly as downloaded from Asus. Also, double-check that the file is in the root directory, not the "Download" folder.Stuck on Asus Logo: This is common after a major version jump. Boot into recovery and perform a "Wipe Cache Partition."Downgrade Issues: Moving from Marshmallow back to Lollipop is difficult and usually requires a factory reset and specific downgrade tools.

Asus ZenFone Selfie (Z00UD/ZD551KL) firmware update to Android 6.0.1 Marshmallow

This is the easiest method if the update is still being pushed to your region:

: A battery-saving feature that significantly reduces power consumption when the device is stationary and not in use. Google Now on Tap