I have a customer that has tried and sent back a fuel cell forklift. It is impractical at this time. The truck required a trailer outside to produce / store the hydrogen, and the truck had to be refuled often since it was using a same size tank as the LPG lifts. Hydrogen doesn't liquify until around 25 degrees Kelvin, so in order to pack as much fuel as a LPG truck into the same space would require obscene cryogenics + pressure (not real practical)
so what happens is that you can only store it in gas form rather than a liquid like propane.