I don't know for sure but as he's a bit older you might need to take it slowly and do it as you would with a pup. Make sure he doesn't see it as a punishment.
Maybe start off by feeding him in the crate and always leave it open. Maybe put his bed in it so it becomes his santuary when he's tired and wants some piece and quite :roll: .
Definitely leave him in there for short periods of time at first and build up slowly. (Don't give up to the sad eyes though - he's only foolling you
).
Let us know how you get on.