It's not a matter of the collar working or not. He needs to learn that it is okay for other dogs to walk by when you guys are out and about! A Halti might prevent his barking, but wht you want is to prevent him from WANTING to bark. See the difference? You need to modify his behavior.

When you see another dog approaching, perhaps you need to make him sit, and keep him focussed on you. Run him through "sit," "give paw" or whatever other commands he knows. Let him know that you are in charge, he doesn't need to protect you. When the other dog has passed successfully, without him reacting, reward him (lavish praise or small treat). Whatever technique you try, you need to be absolutely consistent, okay?