wifi greyed out

If the Bluetooth button is also greyed out in the Settings app your phone’s hardware has failed; specifically the radio chip that provides both Wi-Fi and Bluetooth. If it is only Wi-Fi you can try to reset network settings:

Open Settings

• Tap General
• Tap Transfer or Reset Phone
• Tap  Reset
• Tap Reset Network Settings

This will erase all Wi-Fi passwords, but will not result in any other data loss.

If this does not resolve the problem it is still hardware, and whether it is worth the cost of a repair vs getting an ew phone is a judgement call.

OK, that means that the screen repair messed up and damaged the Wi-Fi antenna. If Apple replaced the screen they will fix it. If it was a 3rd party shop you are out of luck.