I downloaded the azure flute, beat the pokemon league, and unlocked the national dex. When I went to Spear Pillar like the website said, nothing happened at all.
You need the national Dex to unlock this event. There are 60 more Pokemon in Platinum than in Diamond / Pearl, so go here to make sure you've seen all of these Pokemon:
If that's not the problem, then unfortunately, I have no other solution. =(