Hey there Champ4202,
Thanks for reaching out to Apple Support Communities. I understand you’re not able to turn on Wi-Fi on your iPhone. I’ll be happy to help with this.
Restart your iPhone and check for any updates as well:
Restart your iPhone
Update your iPhone, iPad, or iPod touch
Then try to connect to Wi-Fi through Settings. This link can help:
Connect to Wi-Fi on your iPhone, iPad, or iPod touch
If it’s still greyed out, go to Settings > General > Reset and tap Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you’ve used before.
If the issue continues after that, back up your iPhone and restore it to factory settings with the steps here:
How to back up your iPhone, iPad, and iPod touch
Restore your iPhone, iPad, or iPod to factory settings
Test it in that condition. If Wi-Fi is no longer greyed out, restore your backup and test once more:
Restore your iPhone, iPad, or iPod touch from a backup
I hope this helps.