Asus Zenfone Max 3 ZC520TL not finding the android 8.1 update.

[Sierra2]

So my Asus Zenfone 3 Max ZC520TL is in android 7.0 and it wont find the update to android 8.1, and i need that update with urgence to give to a friend of my because his phone is broken, the phone in question is in firmware WW-14.10.1808.119 the Android 8.1 update for that phone is WW-15.10.1810.275

Yes, that phone got android 8.1 i have some friends that have the same phone and same model with that version.

How i update it to android 8.1?

[Falcon_ASUS]

@Sierra2 
We would like to inform you that we no longer provide previous firmware versions or downgraded software packages on ASUS official website. This is to ensure that the security updates on your phone remain up-to-date with the latest firmware versions. We appreciate your understanding and patience. If you have any question or need assistance, please feel free to visit our service center or call the service hot line, we will do our best to provide help for your questions. 

If you have a need for a system upgrade across versions, we recommend visiting a service center where our staff can assist you. 
You can find service center locations at the following link: 
https://www.asus.com/support/service-center-location
Sorry for any inconvenience it may be caused.

[gramwilliams]

 The 8.1 update is real but slow to appear. Grab the WW OTA file and install manually via System Update.

[Sierra2]

Nope, the file i need and the websites that have, force me to pay to get for it, and i don't want to pay for it, the system update doesn't find anything