Audio Help

i have just a regular factory cd player in my 92 explorer although i dont think it was the original one in the car anyways...it turns on fine and recieves stations fine...however, there is no sound that comes out...checked the connections at the speakers...seem to be ok...

pulled out cd player and checked the connections in the back...has three connections antenna, a long rectangle gray plug and then a smaller square one that attaches right next to the gray one...
am i missing a connection?

will one bad connection to a speaker make all of them not work?

any tests i can do to find out whats wrong?

thanks

if you have it out, can't you move around the wires to see if things are working?