To be honest I don't remember the route, but choosing his route means his is your partner. Maybe you haven't finished rune and burry routes. Because you can't start his unless you do these two first
Viewing post in Shelter (Furry Visual Novel) comments
(https://rausmutt.itch.io/sheltervn/devlog/934733/shelter-flowchart) yep you can continue his route after them and you will see his cg. this is the flowchart if your struggling with anything