Hi:
Are you working from a SAVED image or a FRESH image? Typically, with a SAVED image, we see instances where the services do not always start up. It is useful to go into Cloudera Manager and check the services before you get started.
If you are working from a saved image, you will always be in safe mode. When you are working in safe mode, you can also get the JDBC messages, connection refused messages and other messages for server04.demo.sas.com.
Please use the information in the Troubleshooting Issues with the Virtual Lab document to restart the Hadoop cluster. This should resolve the issue and takes about 15 minutes. You'll find the document when you first enter the SAS and Hadoop e-learning course:

After opening the doc, please follow the instructions on page 2, How to Verify or Fix Hadoop on the Hadoop Collection:

If this restart doesn't work for you, then the instructors recommend starting with a new reservation for a FRESH image.
If Lesson 6 was where you first experienced the issue, then that is what should be reported. Until the image issues in Lesson 6 are resolved there's not any reason to move forward to Lesson 7 on the same image. When other Data Curation students have reported the same error message as you show, either a restart or using a FRESH image has resolved their issues.
Cynthia