The POR strip uses a pump action spray bottle. Could the stripper have some gel in it that is clogging the sprayer? When you pull the trigger, is there a lot of pressure against the trigger or does it feel like it's free-wheeling? I think a lot of pressure would indicate a plugged nozzle, no pressure would be a plugged pick-up tube.
Their catalog shows an adjustable spray nozzle, if you've adjusted on it, take it off to look inside (but don't shoot yourself the the eye!)
But then again I could be wrong. I was studying electron flow instead of spray bottle theory.