Well I'm sorry to say that the odds of the floor coming clean are not good. This stain could be from a of couple things, the stains could be from a rubber mat or carpet that was down and some one tried to get the stains out by scrubbing it with an abrasive pad. If an abrasive pad was used and scratched the floor, the vinyl becomes porous and absorbs dirt and stains the floor permanently. The finishes on vinyl flooring are much like the clear coat finish on a car, abrasives will ruin the finish and maybe the floor.