WiFi greyed out and won’t connect to internet ?

Reset Network Settings: Only network settings are removed.

• When you reset network settings, previously used networks and VPN settings that weren’t installed by a configuration profile or mobile device management (MDM) are removed. Wi-Fi is turned off and then back on, disconnecting you from any network you’re on. The Wi-Fi and Ask to Join Networks settings remain turned on.
• To remove VPN settings installed by a configuration profile, go to Settings > General > Profiles & Device Management, select the configuration profile, then tap Remove Profile. This also removes other settings and accounts provided by the profile. See Install or remove configuration profiles on iPhone in this guide.
• To remove network settings installed by MDM, go to Settings > General > Profiles & Device Management, select the management, then tap Remove Management. This also removes other settings and certificates provided by MDM. See “Mobile device management (MDM)” in the iOS Deployment Reference.
• Reset your Network Settings. Tap Settings > General > Reset > 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 above fails...

Reset All Settings: All settings—including network settings, the keyboard dictionary, the Home screen layout, location settings, privacy settings, and Apple Pay cards—are removed or reset to their defaults. No data or media are deleted.

1. Reset All Settings: Return iPhone settings to their defaults - Apple Support:- Return iPhone settings to their defaults
2. You can return settings to their defaults without erasing your content.
3. If you want to save your settings, back up iPhone before returning them to their defaults. For example, if you’re trying to solve a problem but returning settings to their defaults doesn’t help, you might want to restore your previous settings from a backup.

Most likely it is hardware. To be sure restore your phone to factory settings using your computer and check before you restore your backup.

See➡️Restore your iPhone, iPad, or iPod to factory settings - Apple Support

The button in the Control Center does NOT turn Wi-Fi on and off. It disconnects from the current Wi-Fi network, but leaves Wi-Fi on if it was on.

Go to Settings/Wi-Fi; can you turn it on and off there? Then go to Settings/Bluetooth. Can you turn it on and off?

If you can control it in Settings then it is working normally.

If NEITHER Wi-Fi nor Bluetooth will turn on your phone has a hardware problem with the radio chip.

If neither Bluetooth nor Wi-Fi work your phone needs repair. Use the Get Support link at the top of this page.

Go to settings and turn wifi back on.