If the channel isn't published yet, then yes, "Refresh Now."
If your channel is published, in my case at least, it automatically refreshes 3 times a day; you can see the times that they have been refreshed. I don't have any manual control to refresh my published channel.
So, I created a mirror channel that I do not publish, where I test my JSON file (with a different name). I "refresh now" and if all goes well, I upload my JSON file for my published channel.