Don't rush your dog, keep him/her away from the bangs, and get him/her out regularly on scent of any type, let the dog enjoy itself. It will take time, it happened to my dog (14 month old), spooked whilst up in Scotland shooting, no apparent reason, ran off and hid, could have been the strange surroundings?
I stopped shooting over her, but took her beating, no problems, picking up no problems, she was not concerned if the gun shots were more than 50-60mtrs away. After a season away from shooting over her, I went out let her hunt up a pheasant dropped it in front of her and have never looked back, the excitement of the chase, nulifies the bang.
Best advise is patience, dont rush it.