Bark Control

I bought a PetSafe ® Innotek Rechargeable BC-200 dog bark control shock collar and I can not get the gray plug?
I bought this thinking and have charged enough. There is a gray cap means I have to connect it is loaded but I can not fit.
I will take you back to the store and tell them the problem, and will probably allow the exchange of the same. Also, do not let anyone tell you shock collars are cruel. I had to use a couple of times, and it worked very well. I have a dog that is stubborn. All my other dogs I trained to not bark, but this is a mucus. Anyway, that responded well to spray guns, and we had no problems. Then My husband's nephew stayed with us a couple of months, and the barking back, and water pistols did not work. So we have a shock collar, and the next day I had a better dog.
Bark Collar Review – Petsafe Big Dog Nano No Bark Collar