I keep getting this error from the challenge.  I logged into my developer console from the Trailhead challenge screen using same email address (only have one on Salesforce.com) and nothing has changed since I started the developer track on Trailhead, which requires numerous challenges.

The Apex class named StringArrayTest shows up on the development console and from the setup interface in the developer section....

I am puzzled how it can show up on both and after entering from the trailhead challenge logon to developer edition and still have this error that is is not  found.  Any suggestion????

I'm having trouble with the Automating Time-based Actions with Workflow which is part of the Process Automation module. I have tried recreating this workflow in 3 new DE orgs with no luck. I still keep getting the same error. "Challenge not yet complete... here's what's wrong: 
Case escalation failed to execute correctly."

I'm sure it is something simple that I'm just overlooking but any input would be great. Below is a screen shot of the workflow rule I have created.