Left speaker don't work

I bought this new North Peak and found the left speaker does not work. The speaker is good (I tested it) and the wiring from the radio to the 4 strand flat wire is good, and the connection under the trailer ( at the slide) was tested and good. I noticed the 4 strand wire runs forward and the speaker wire are of a different type of wire leading me to believe that there is another connection somewhere before it goes to the ceiling.

Does anyone know how the speaker wire are run from the slide to get to the ceiling? That will help me from taking the whole bottom off to track the wires

Thanks