Why can't I update the firmware?

mie

I have VMG3625-T20A and it has a firmware version V5.30(ABIE.3)b2_E0. I've tried to update it to 5.30(ABIE.4)C0 that I have downloaded from the website of Zyxel. I extracted the file and tried to upload it but I got an error message: "Image uploading failed. The selected file is an illegal image. You may press 'Cancel' to upload another firmware image file, or press 'OK' to reboot to recover normal operation." What can be the problem?

#CPE_Nov_2018

AAAAL

Hi mie,

Your current firmware V5.30(ABIE.3)b2_E0 is a customized firmware version, generic firmware 5.30(ABIE.4)C0 cannot be suitable for your VMG3625-T20A. 

You can connect to your internet service provider for the firmware upgrade requestment.