I have some jet lighters in my shop. I’m not a smoker but they are useful for other things too. My problem is that they seem to not work at all?

When I buy them they are fine, push the button, clear “click” sound and a fine hot jet of fire. After a while though, they simply won’t fire anymore, even though the little window shows that there’s plenty of gas inside.

Are these also using the normal propane/butane as regular lighters?