My horse doesn't understand me - do I reinforce the aid or do I change it?

Do you remember the post about talking with the ears? You find it here. This one is the sequel.

I‘d suggested to look at your horse‘s ears if he doesn‘t react to an aid. If you see them pointing in your direction, you‘ll know that the horse is listening and trying to understand you. If he doesn‘t react appropriately it‘s because he is unsure what to do. So instead of reinforcing and repeating the aid (he already hasn‘t understood the first time), it‘s worthwhile to think about how to help the horse understand what you want by changing the aid.

Now how can we change it?

I recommend to look at the following: