Your regulator has developed a creep issue not uncommon after a few years of good use.
That’s why your regulator is showing 100bar & the hammer is no longer strong enough to open the valve.
Just unscrew the bottle & then take a spanner and very slowly unscrew the back gauge for the regulator until you hear the air bleed off slowly, leave it until all the air has escaped then nip the gauge back up to where it was, you’ll probably be able to hand tighten it back to the same position once the pressure has gone. Or take a 2.5mm ball end allen key & turn the regulator adjustment screw counter clockwise a little, the air will also bleed off slowly via that method too.
You need to buy a rebuilt kit and replace the piston, belleville washers & pressure adjustment screw. It’s really not that hard it just sounds it.
Happy to help where I can if needed.