I am not able to access one specific Trailhead - https://help.salesforce.com/HTTrainingModulesDetail?courseId=a1S30000000isKDEAY

INitially i was able to view the video but not take the quiz. Now I can't view either the video or the quiz. I get the error message:
Error: We are experiencing system errors, please try later

Please note, I am able to access other badges, view videos and complete the quiz e.g. https://help.salesforce.com/HTTrainingModulesDetail?courseId=a1S30000000hqlb

Thanks.

I had to create a Developer Edition Org under a different username for Wave Analytics as I was informed while filling out the form that I could not use the existing username. I have been able to complete all the functionality using the Developer Edition Org. Except I cannot complete Hands-on-Challenge. My 'network salesforce' username where i am taking Trailheads does not recognize the username used for Developer Edition Org. I get below message. Please let me know how can I reconcile this issue. Thank you.

Challenge Not yet complete... here's what's wrong: 
The 'Trailhead_Data_Manager' app was not found. Please follow the requirements and ensure the wave enabled org is setup correctly.