Why I can't award bounty points?

Question

I got a great answer for this question Number of China orbital launches by year

Then I put a bounty and chose "Reward existing answer"

But I cant give the points to that user, why is that?

Later edit:

I started a few more bounties, I get the same thing, the bounty points button is in gray and I can not use it.

Answer 1

Did you wait 24 hours after starting the bounty before trying to award it? There's a waiting period before you can give it out.

From the FAQ on Meta Stack Exchange:

How do I award a bounty?
A bounty can be awarded 24 hours after the bounty was started.