For manual update, you download the file from the asus support site, copy the file to device memory, restart it and the update prompt will appear. If you have questions there are tutorials on youtube showing the procedure on other Asus devices.
Para...
Gilson.dcl
Try upgrading to the latest fw available on the support page.
https://www.asus.com/us/Phone/ZenFone-3-Max-ZC520TL/HelpDesk_Download/
(Version TW-15.12.1810.35
2018/12/07)
or search for OTA update on your device. to try to fix this problem ...
