My rear door speakers on my 745 suddenly stopped working. I had recently replaced the red bulb failure relay just under the radio, but that is the only thing I think I could have done that might have affected the radio (it's a CR718). Is there a connection I might have unplugged?

I have tried to take the radio out to take a better look, but there is a metal bracket screwed into each side of the radio that is preventing me from getting it all the way out.

Thanks