Hi,
Couple of things to try first if you want to try them of course and see if either resolves the problem.
a) Clear the phone’s cache partition. ''(wipe cache partition)''
Here’s a [https://www.asus.com/zentalk/thread-215476-1-1.html|link] that shows how to do this.
'''''DO NOT select wipe data / factory reset''''' ''as this will erase all your data and downloaded apps''
b) In the phone navigate to ''Settings > Reset > Network Settings Reset''.
This restores WiFi passwords and other network settings