Standard practice for sheet floor coverings in RVs is to let them float, not glued down. Installation is a stretch, then staples tacking the edges.
Stuff gets installed on top, also fastened to the floor, such as cabinets, dinettes, other furniture, sometimes even water tanks. I suspect your floor wasn't stretched well enough, installing and screwing down furnishing pushed the slack into a bubble. Maybe even before the walls went on.
I suspect Fleetwood is not going to back up to the point where the floor was installed, to stretch it properly and tack it down again. That could involve removing everything inside, taking off roof and cap to remove the walls. Fleetwood just isn't that sort of company.
Best you can expect is some effort to flatten and glue down the bubble, but with too much vinyl pushed into too small a space, fix is unlikely to be permanent.