Why can't I delete animator parameters?

I don’t know why I can’t delete the parameters. I’ve tried right clicking, pressing the delete key, pressing command and delete, and when I click ‘Edit’ on the top menu, “Delete” is grayed out. I was always able to do it with no issues but now nothing’s working. 113750-screen-shot-2018-03-26-at-24715-pm.png

Right-click on the text of the animation parameter (e.g., isRunning) and then select Delete.

for mac

(fn left bottom button on the keyword)