Why would Ash give away Infernape? That doesn't make sense, even if Paul is a better trainer than before and a better person, Infernape belongs to Ash.
Actually, the last time we saw him was in episode 1136 or #47 of JN, the Pokémon Eating Contest where Goh participated with his skwovet now a Greedent, I know it was filler but we saw it.