1) He's an App and app's are SUPER smart and get bored SUPER quick. Sometimes they just need a break from same 'ol same 'ol. Come up with new and weird things to teach him and he will probably love to be around you, otherwise if it is the same circle day in and day out... well, he would rather be in the pasture.
2) He's green so expecting him to move off more than a few strides is asking to much.
3) A green horse has to learn how to balance himself first, then you on top of him. If he is not confident he will falter and falling into the canter tends to make them less confident.
I would recommend not 'beating' him into the canter, however, set him up for success. What I mean is if your verbal cues aren't solid, get them solid. He needs to know each time you ask him to move off what you want. And a greenie is not going to know by your leg. once you get that stride you want praise him like the sun just shone after 2 weeks of rain. Let him rest. Let him think about it. Release should be slow down for him that is his reward. After a few minutes chill time ask him to move out again. Each time he is praised after an extra stride or two. Before you know it you are around the arena. Never be in a hurry with a greenie. And always be willing to go back to basics
4) The hill trick and friend trick work great. Also when you get the canter up the hill let him rest and PRAISE him like there is no tomorrow. Some believe that rest is enough praise but I have found if your horse is fond of you and they get a lot of love for doing something that please you they tend to do it more.
5) I don't know how good a rider you are, so PLEASE don't be offended. How good is your balance at the canter? Have you been watched by an instructor yet or recently on a seasoned horse?
6) Has your saddle been checked? We were trying saddles on one of my horses it seemed to fit fine. A friend rode her in the arena no issues at walk/trot. I got on the horse and we rode around and did a few circles but the moment I asked for the canter she reared and crow-hopped. First time EVER. I got off immediately this saddle was being used on another horse and he had recently developed similar issues at the canter. Told the owner, different saddle no problem.

Mmmm... Apples!

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