Undercarriage plastic liner Is coming loose lots of plastic bolt missing floor feels soft.

If you're referring to the plastic shroud that goes all the way around the underside rear of the car and the wheel wells, mine was missing all the fasteners from the factory. Apparently they also missed it when prepping the car at the dealer. I didn't notice it until I was at the car wash. I went to a dealer closer to my home and they wouldn't touch it, saying it's not a warranty issue--it's a dealer prep issue and I needed to take it back to where I bought it. I took it back to the dealer where I purchased it and they installed all the fasteners and apologized profusely.