To add on to what JKH said, I can think of a few minor things that could make an elevator "skip" a floor. Without going into too much detail, the call could be broken, floor position system could be malfunctioning, or you simply did not pray to the elevator Gods correctly, and as such, they found you unworthy of giving a ride.
I appreciate you asking in a non specific way, and I hope our non specific answers help. We at times have issues diagnosing problems on equipment right in front of us, that we can touch and test... No real way we could do much more than guess, though some are Very Very educated guesses, here on a forum.
