Had one for a short time befoe i seen the light and got a 12l 300bar bottle.
When i used it on my s410 i had to cock it first. And obviously make sure the bleed valve was closed before pumping.
Is the needle moving on the pump gauge.
First 75 to 100 bar should be relativly easy to pump.Then it gets a little harder,that is actualy when you start filling thr cylinder
hope this helps as i said only had the hills pump for a wee while
otb Brian