Try taking an older dog that will run a track and see if she will follow. If not double snap them together about a ft apart and let the older dog lead her to the pig.
Most of the time this happens for lack of confidence in a young dog.
Your pup is not independent enough yet to leave you.
Some dogs are just naturally born to roll and others take time with alot of repetition.JMO
x2 should work with a older dog