How have you reintroduced jumping to him? Just so we can get a clearer picture.
My advice would be to take it as slow as needs be. Do lots of trotting poles with him, then put a flat tyre (or any other low object) under the one side of the trotting pole, raising them on one side so he can think about where he's putting his feet. Then start off small, very small, with simple crosses, just one at a time until he is clearing those happily. Then two, but not close together. Then slowly introduce him to a double. I usually leave the first jump of the combination down at first, so its just a pole/two poles lying next to each other on the ground between the uprights and trot him over that and then into the second part of the combination which is a small cross. Dont make the combination too short to begin with, give him three to four strides to let him work it out. I do this at a trot, and then at a canter. Once he's happy with that, put up the first part of the combination and let him go over that.
The point is to go slow and build up his confidence as refusals teach him bad habits. By taking it slow, you reduce the chance of refusals and give him time to happily find the jumper inside himself again! Once he is happily jumping the combination, shorten it, keeping the jumps short, eventually reduce it to a one strider (you might need to put the first fence down again to just the poles on the ground to give him the idea) and eventually to a bounce fence.
I like to keep fences low and do them at a trot first before doing them at the canter, I find it keeps the horse a bit calmer (some horses in my experience tend to rush into jumps at a canter) and gives them more time to work it out. But trotting poles and cavaletti really do help in the beginning! I also found that lunging over jumps sometimes help but I usually prefer tackling the problem in the saddle with jumping.