My friend asked me to fix her phone because she can't turn her wi-fi on. When I tied to turn it on it says: SMART NETWORK SWITCH This feature is disabled because mobile data transmission is disabled This wasn't written in English so I had to translate it. Hope you understand and can solve the problem. She can use data and connect to the internet but that's too expansive. Its a galaxy phone (s2 or s4)
"mobile data transmission is disabled" Go check the settings on that. Something must be off ( or on if it's something like a firewall, etc ) Google says it's the setting under Wifi > More > Smart Network Switch
use this guide but you turn it on https://www.howtogeek.com/256663/ho...-network-switch-to-avoid-too-much-data-usage/
Smart network switch was new (and buggy) in android 4.3. it's supposed to autodetect when wifi is unavailable and switch to cellular data. If she doesn't intend to use mobil data since it's too expensive, then there is no need to have smart network switch enabled. Disable it and manually control the wifi.
Try checking the data saver&accessibility setting. My mum's net and wifi went down several month ago and i found that the data saver app was actually preventing it to connect continously to the net. I don't really know though, mr. Google is a better option for tech things I'm using an old S3 but i haven't encountered that problem yet