They gather in Twilight's Castle, looking at their solved puzzles.
Twilight shakes her head. "They couldn't all be in Ponyville, could they? Well, I don't care if we have to travel all over Equestria. We're going to find this friendship problem."
They leave right away. It's going to be a long trip.
Where is the friendship problem the Mane 6 need to solve?
Start at the star.
Hints are available here.