Antenna a pretty simple so they generally don't fail. Basically they are a piece of wire of a certain length. Sometimes the screw on connection breaks from the wire but it would be unlikely that you have multiple failed.
Some machines have wires that go from the connectors on the back panel to a card in the machine. Maybe one of these has come loose or is not connected to the wifi card. Not all wifi cards have wires some connect via the circuit board so loose wires are not a issue.
Antenna a pretty cheap so I guess if nothing else works you could pick up some new ones. You need nothing special most device use 5db antenna and the connection is standard.