pull a compression test and come back and show us your results
if compression is good it should be up around 125-150 psi on each cylinder.

Run the test a 2nd time , make sure you put a shot of oil like wd40 or something in the cylinder(s). I always do a dry and wet test to compare just in case of possible ring/valve issues.

If you have compression, spark, air and fuel there is no reason why that cylinder shouldnt fire. Unless there is some kind of obstruction in the intake not allowing fuel to get to that cylinder. And yes, as bigG said, it gives you a better reading on comression testing if you remove all the plugs first, less drag on the engine :o)