So everyone is talking about how they got domeat down in the damn vault and got this dope gun! Well I can't!!!!! Why is that? I got Codsworth ass down there! Is there any specific kind of placement or anything special u gotta do to make this fury mudda down there???

I had just got Dogmeat as a companion. I went to the elevator and when it loaded the vault Dogmeat was waiting for me at the bottom.

Did u put him in the circle at all or no?

No. He wouldn't get on the elevator. I just hopped on and he was waiting for me outside the gate when it stopped. Same thing going back up. I thought I had left him behind but he was waiting for me again.

Do you have him set as your companion?

Click on him to make him go places then walk on the the lift he should be at the bottom when you get down