I would take him out on his own to see how he acts. Carry some treats and sneak them to a person. Have them tempt him with it. Also if you have some friends ask them to help out and greet him on a walk with treats.
Also they can go thru a fear period, just dont use babytalk to comfort them because it will reinforce the fear.
Also they can go thru a fear period, just dont use babytalk to comfort them because it will reinforce the fear.