I had the same problem camped at ~9000ft. Here's what I did to fix it (YMMV): I opened the little view hole and unscrewed the sheet metal casing around the igniter. Got it lit and then screwed the casing back on leaving the view hole open. My theory is that the lack of oxygen would make it hard to light and stay lit - the open hole allowed more air. I ran it this way for a week.
__________________
|