What brand switch was it? I have ran into a few problems with some of the Wells ignition lock cylinders, I have much better luck with Standard ignition products,Wells is sold predominantly at Auto zone stores.
No , they only go in the switch one way, was the cylinder turned back past a accessory when you slid the cylinder into the switch? Possibly just a bad cylinder, maybe one tumbler has fallen out, was your old cylinder bad? or broken?
This is the original tumbler in a new switch. the tumbler works fine when out of the switch. When it was in the old switch and turned to start it would not come back from the start position unless you turned it back like a broken spring or something.