It will take a week or more for the system to complete the auto push the FOTA update. If you any issue (like out of Wi-Fi coverage area) updating your ZenFone 3 (ZE520KL) to latest version (14.2020.1711.80), you can download the update to your PC and install manually as described below.  

If you have not received the OTA update notification on your device yet, check it by going to Phone Settings > About > System Update > update manually. Alternatively, follow the below manual installation guide. What is new in 14.2020.1711.80 (ZE520KL)? If you prefer manual installation and before proceeding with below steps, back up every data you have on the phone. Also, make sure at least 2GB free space remaining on the SD card. Also Read: ZenFone 3 Zoom (ZE55KL) Starts Getting Asus’s New ZenUI 4.0 Update

Download and Install 14.2020.1711.80 Update on Asus Zenfone 3 ZE520KL

Important: This guide is for Zenfone 3 ZE520KL and SKU WW. Do not install the firmware on other SKU (CN, TW, etc.). Check it by going to Settings > About > software information > Build number and see the software version for WW, CN, JP, etc.

  1. Download 14.2020.1711.80 update for Zenfone 3 ZE520KL from here [download WW version]
  2. Rename the downloaded firmware file to ‘update.zip’ and save it on your phone.
  3. Boot your phone into recovery mode (Switch off the phone and turn on by pressing Power + Volume Up buttons together).
  4. In recovery, choose Apply update from sd card and then select the update.zip file.
  5. After completing the installation, reboot your phone. (Source)