Why won't my iPhone connect to Wi-Fi or mobile data?

my wifi just isn’t working on my phone. when i “connect” to a wifi using settings it doesn’t show the wifi symbol next to my battery and it just doesn’t work. i tried to see if it works on other devices and it did, it just doesn’t work on mine. when i try mobile data, it didn’t work either. i also tried joining a hotspot from another device i had but that didn’t work either. how can i solve this issue?

[Re-Titled by Moderator]