My 7 month old yellow lab is great when we take him to an off-leash park and walks along nicely with us, but when he's on-leash in our neighbouring streets if he sees another dog he'll immediately sit down and become an immovable object.
We've tried commands, treats, almost dragging him along (which can't be good for him and makes us feel like mean owners),
He's got a great friendly disposition, but can also be nervy in the dark early mornings/late night walks and as well as other dogs, sometimes will sit if he sees another person/squirrel/bird/movement of any kind.
It doesn't seem an aggressive thing, sometimes when they get closer he wants to play or he'll just continue lying there.
Any ideas how to entice him along? I think that a 2nd round of training may be in order.