After Android update (V12), WiFi is no longer recognized

For the sake of forum categorisation I’ll assume this is about a Fairphone 4.

Some generic things for a start (I don’t have a Fairphone 4) …

Did you already try to turn off the phone (not just a reboot, real shutdown), wait a few seconds, then turn it on again?

Else … there should be a “network reset” available somewhere in the Settings (search the Settings for “reset” and go with “Reset Wi-Fi, mobile & Bluetooth” or similar).