I was watching the anime ( ADEVENTURES IN SINNOH if any one was wondering) he can easly capture the pokemon there so has he ever failed?
Many many times. The first time was when he tried to catch a Pidgy in the first episode, it was an epic fail because Pikachu was being uncooperative. An example in Sinnoh is when he was trying to catch Buizel, he failed, but Dawn succeeded and eventually trades it too him(Sorry if I am spoiling anything).
i remembered that he failed to catch a deerling during the unova series and i think he wanted to catch a minnicino...or was he trying to get his gym bage holder back(dont really sure if its called that way)