How do I select ‘equal’?

[Nuhyell]

I was going to select that three circles and equal while learning a tutorial, but when I selected over a circle, disappeared that button. How can I do that?
I attached about that video, please check it.
I would appreciate if you let me know.
Thank you.

[DanielR]

Hello - your circles are on a different plane (if you look closely at the bottom two circles, they look faded)

If you want to apply a constraint, make sure your sketches are on the same plane