If your dog could talk what would he be saying when you called out "Come" (or whatever word you use to call him to you)?
"I know what you want, but I'm too busy" or "gladly. Here I am"
Ruby was the "gladly. Here I am." Right from a young age she would bound up to me the instant I called her.
Blaze at 15 weeks is the "......I'm too busy." Yeah he's still young but I believe he should be coming when called by now. I'm a great believer in the instant recall, as it can be a life safer if they are getting into trouble and you need them instantly.
What I had done with her is right from a young age when she was still following me around was say come and treat her straight away with a food treat and praise.
What have I done differently with Blaze? Nothing. He's just a little bit more preoccupied. lol
I am always thinking of new things to try when it comes to training. Because if one thing doesn't work for a dog you may have to try something else.
Positive Reinforcement is the best thing to use when teaching recall. Or anything for that matter. I asked my 2 younger children to come outside while Blaze was outside playing and gave them both a handful of treats. We all stood in different parts of the yard. When Blaze came near me I said "come" and showed him the treat as I walked away. Then I got one of the children to yell out come and offer a treat straight after he took the one off me. Then got the other child to do the same. We kept doing this a few times, then lengthened the times between the calls. We got to five minute intervals between each "come." Then we moved inside, and went to the door occasionally to call come. He would come instantly. A few days of this and he is now coming when called. We will keep this up for a couple of weeks. Just longer intervals between the "comes"
We got him to think "Ok, I'm busy, but I know its good to go to them when called so I'm going right away."
Thats what works for most training. They will do something if they know there is something in it for them. Gradually the treats can be given less and less until only giving every now and again to keep their interest.
When training with treats like this though, It is a good idea to take it out of their daily food ration or you will end up with one very fat puppy.
You could do the same with one person. Call them come when you are close to them. As soon as they take the treat and start to walk away call come and treat them again.And so on. The trick is to get their mouth watering every time they hear that recall word.