When my horse was beginning his training, my trainer would lunge him and have him associate voice commands with the different gaits. She also worked on getting him to move off of pressure. When he began being ridden under saddle, he understood leg cues and also voice commands, so when she would apply the cue, she would also say the command, and he began to associate the gait with the leg cue. The first time he was cantered under saddle, it was done off of a small crossrail to get him to naturally pick up the canter rather than making it into a huge exciting event. For the next few canters under saddle, my trainer would apply the cues and say the word canter, and he picked it up. Now he is cantering perfectly under saddle. I would try going back to basics. I know you may want to show and jump, but sometimes we need to take a few steps back in order to get a better overall picture. You can’t rush good training!