My Paslode 900420 will not fire after service

[guymad]

Hi
I have a Paslode 900420 (LM350) nailer which has been perfect for ages and never failed but thought I would do a service - took it apart as per instructions - cleaned it . degreased it, oiled it with paslode oil, replaced the 2 O rings. Put back together.
Tried it and did not fire.
When I pushed the head down and pressed the trigger the fan started and smelt of gas, the LED light flashes green and new nails in rack. But did not fire.
Took it apart again reassembled and again all seemed to work but did not fire.
What have I done wrong?

 

[guymad]

I have cleaned it again and double checked the spark unit and all is fine ( good spark when trigger is pulled and micro switch is pushed down).
I have purchased a new paslode gas with date out to dec 2012 and now tested the unit- cycles perfectly but does not fire - now really stuck!
help!!!