Running for running

Why do pneumatic reclining office chairs suddenly stop reclining, and how do you fix it? - raised chairs

I have a couch in my office, desk, a work of imagination with a tire lever that raises and lowers. It also has a button on the bottom, with no known function - which has an arrow on the right side of the minus and plus a somewhat different.

I have had over a year. Generally based on 30 degrees. Last week was just lying down and I fear that the force does not mean that I will be slightly bruised. I (a little overweight.) Bin

I've tried the little knob on the bottom in both directions, no dice. I have also tried to climb and descend on him, even if it is upside down and shakes it. Just do not bend over.

Help?