This One Time at Space Camp... - S4-E18
Plot hole: When Dr. Hughes is racing to save Allison when he thinks he is Carter from the events that happened in "I'll Be Seeing You" Henry says he is racing for a cliff, and that the cabin was just a hologram. But in the episode the Cliff was the hologram disguising the cabin. Henry even commented in that episode that he did not remember a cliff being there.
Chosen answer: He's still around, we've just not seen him lately, as scenes with Blake have been mainly at work, where Kevin wouldn't be.
Tailkinker ★