Hope you're well.
I am trying to create a gradient background. I've created the gradient but when
I open up the gradient editor to play with the slider the changes I make don't
show-up in the gradient when I click ok. Am I doing something wrong?
Are you using the Gradient Tool or one of the gradient adjustment layers (gradient fill or gradient map) or a layer style (gradient overlay).
The Gradient Tool doesn't update an existing gradient on the canvas.
What version of photoshop?
If you are using the gradient tool:
click on the gradient tool
click on the colored gradient on to top left to enter the gradient editor
edit the gradient as desired
That gradient will be active now and you can use it.
If you want to,you can name it from the gradient editor and click new so it will add it to the visible gradients.
Then if you wish, you can also click save to save all visible gradients in the editor to a preset file.