could be wired wrong
could be blow outputs on the head unit
Could be blown internal amp


If you have access to a small amp then try to wire your speakers to an amp and see if they work. If they do then you have either a fried internal amp and you will need to amp the speakers or you have the speaker wires wired wrong and you need to fix them.

If you have blown outputs then you wont get any sound from the speakers even if they are amped.