Solution
Ensure your mid server is up and validated, with zero issues.
If the MID server is reporting any issues in the 'Issues' related list, please do the following first:
- Click 'Invalidate' on the MID Server page.
- Go back to the list view, select the MID Server and hit 'Validate' from the list choices.
- Wait a few minutes for the MID Server to become 'Up' and Validated 'Yes', then re-try the exercise.