They always give me 'Try again later'.
And if I click on somone I NEVER click before. They either give me fail or success. at least a kind of reply.
the try again later looks like I have 'already' clicked them.

I don't know, since around 3 hours ago, when I feel something is wrong, I already start using SPY to find new people to click on. Occasionally testing on the same person in the thread I go though.

I am trying to get as many as possible because... well, there is the hall of fame. XD one of the fun to get top.
Anyway, I am resting now.