No reception

Squelch may be too high causing it to block incoming signals.

 

Do you least have static?
Like Flatbedn said, set squelch and RF gain till you do.
Still nothing? assume it set to PA or external speaker in wrong outlet.

 

Try an external speaker. Sometimes the internal speakers go bad.

 

IT maybe a mic problem, you need to plug in the mic to make it work but I know you have it plugged in so it could be a broken wire in the cord or a problem with the mic switch itself.

Another CB trick I use when I have this problem is not to worry about the audio but the meter, by first having someone with another radio key their mic and see if you can see the meter move. If you can't, then go to the controls and see if you can adjust the RF gain to see if it moves. If nothing then you want to rule out the antenna, then take a piece of wire and stick it in the center of the coax plug to see if you get a signal.

 

What SWR are you seeing? If the radio did OK in another truck, and I assume with another antenna, then that would be something to look at. I know from experience with Frieghtliner Cascadias that bad antenna systems make a perfectly good radio useless.