For setting custom URL for my YouTube Channel

I am eligible for a custom URL for my YouTube Channel. However, it is not giving this option.
Have 100 or more subscribers.
Be at least 30 days old.
Have an uploaded profile picture.
Have an uploaded banner image.

My channel is https://www.youtube.com/channel/UC1BCcMeBIPwdPHR7-uvCKUQ

I want to change it to https://www.youtube.com/adrakse