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.

If using a microSD, select the firmware file from your card and confirm. Once the process hits 100%, select "Reboot system now." Troubleshooting Common Issues

Updating to Marshmallow brings several functional changes to the ZenUI experience: Asus Zenfone Selfie ZD551KL - Full phone specifications