Hey @itr1718
First off, can I make the comment that asking for people to look over a project and find your mistakes is a big ask and somewhat unreasonable? Very few people here have the time to go through a mass of files looking for a problem and nobody is paid to do it. If you're going to post code and ask people to review, I suggest that you keep it to less than 40 lines so that all of it basically fits in one screen for easy review.
Secondly, I've done what you're trying to do (get the CDC demo working in my project) a number of times. I would suggest that you look at your clocking and how you set it up - when I went to the current SDK with MCUXpresso, I had a lot of issues with clocking (the clock wizard requires a very good understanding of the clock circuitry and patience as you need to hit buttons repeatedly),
To get things working initially, I copied the "clock_config.*" files from the demo into my project. I DO NOT recommend that you do this blindly but it may be a way of move the ball forwards - you didn't say which platform you're getting the demo files from and what exactly is the platform you're working with (You should explain clocking on both platforms).
If you feel clocking is good, post a screen shot of the clock wizard for your project so that it can be reviewed here (looking at block diagram isn't too big an ask).
I know how frustrating it can be to get USB CDC working.
Good luck and let us know how you are doing,
myke