Is there a reason no one is helping me with this?
Aside from the fact that you have very unusual hardware, that not many other people are trying to use together?
You have serial print statements in your code, but you haven't shown any serial output. That makes it hard for us to see what is/is not happening in your code.
All that you have said is "it doesn't work". That's not a lot to go on.
You set pin HIGH at the start of loop. There is nothing in that name that implies what that pin is for. Is it supposed to do something with the MP3 shield?
Some of the code to alter that pin is commented out. We have no idea which group the command is in to play a track, so we can't see if appropriate code is still in place, or not. Even if the appropriate code is in place, does setting the pin LOW cause the whole track to be played? I don't think so. I think that all it does is start something happening.
Then, loop() ends, and is called again. At that time, you turn off the playing of the track, so it is possible that only a few nanoseconds of the track is played, which is not enough of it for you to hear.