How to create a ui action button on a case to create a new task

[Regilio]

Hi all,
I'm struggling with a button on a case form that creates a new task.

The button is visible but I can't get the ui action to function. This is what i got:

Hope someone can help me and guide me in the right direction.
Thank you!

[Ankur Bawiskar]

@Regilio 

Thank you for marking my response as helpful.

As per new community feature you can mark multiple responses as correct.

If my response helped please mark it correct so that it benefits future readers.