WiFi icon not showing on the menu bar and Internet not working (wifi or ethernet)?
Is it possible you inadvertently disabled wi-fi and ethernet in system preferences > network?  If they are not listed in the left hand column of that window you can add them back by clicking the plus sign to 'create a new service' and then setup wi-fi and ethernet.  It's nothing more than picking them from the list of services and then clicking 'Apply'