WiFi Not Working.

Hi

Does a cabled connection work?

If you have other user account does that user account have same issue? if you do not have one then create one and test: https://support.apple.com/en-gb/guide/mac-help/mtusr001/mac

Wifi not showing could be a hardware issue, I would suggest running a diagnostics test to help: https://support.apple.com/en-gb/HT202731

it is important to first determine if the problem is the computer's inability to access your Wi-Fi network or if the network or modem is broke. It is often helpful to turn the modem off, wait several minutes, then turn it on to reset it. As noted above, plugging in an Ethernet connection will allow you to determine whether the modems actually working (and the network its connected to.) Also most internet providers have some good diagnostic tools on their web sites, if you have access to another computer to use them.