When I first began to try to start using YouTube with my already existing Google account, the create a channel button was not working for me (this is in May 2020). When I pressed the button nothing happened.
The fix for this that worked for me was to add and save my first and last name to my Google account (in manage personal info). After doing that info update, then the “create a channel” YouTube button worked great!
So, if you’re wondering why clicking on that channel button doesn’t seem to do anything and how you might fix it, hopefully the the steps above will help you. Good luck and have fun creating and sharing videos.