I continue getting an error on the Workflow Rule in the Trailhead excercise that says a workflow field update action was not found, but I have created it.  

Challenge not yet complete... here's what's wrong: 
The 'Set Case to Escalated' Workflow field update action was not found.
Create a workflow rule that will update a field.In some instances, a case must automatically escalate. Create a workflow rule that will set the escalated flag and send a task to the case owner, if a case is not closed and its priority is set to High.

Can someone please help me with this? What is the correct formula for the workflow itself? Perhaps the error is in my current formula.
Thanks!