The seat doesn't go low enough.
Cut the seat post shorter. You can shorten the post with a hack saw easily, just make sure there is always 2.5" of length in the seat tube. Any less can cause a failure in the frame
This is actually by design, In order to accommodate the rear suspension, Full suspension bikes have less room to fit a seat post inside the seat tube thus the seat post will bottom out in the tube but in order to not limit the max height, the post is uncut.