On any ball lock keg, regardless of size, the post with notches around the hex or 12-point wrenching section indicates a gas post.
Might be a good idea to remove one of the posts and confirm you placed them over the proper dip tubes. Sticking a gas post over the long dip tube will definitely result in a bad time
I actually carbonated this one with sugar and didnt want to release the pressure. I did put the gas on the correct post ( yeah me)! Thanks for the help. 11 month old barrel aged English Barleywine taste fantastic.