Why can’t I connect with Wi-Fi?
If you’re having trouble connecting to a network that’s existed for a while, try restarting the router or
switching Wi-Fi on and off again. If you’re still having problems, go to the Network pane in System Preferences and make sure Location is set to Automatic. If that fails to resolve the issue, click the Advanced button, then remove the Wi-Fi network you’re having problems with, then try connecting to it again. Also, ensure ‘Remember networks this computer has joined’ is checked.