How to resolve an error when submitting verification for a module.

I'm on my final trailhead Customize a Salesforce Object | Create Validation Rules and the following error message is given when the Verify step to earn 100 point "An unexpected error occurred while inserting Opportunity records and we couldn't check your work. Make sure Opportunity records can be inserted in this org, and click "Check Challenge" again. If this continues, contact the Trailhead Help team."

I refreshed everything and attempt to verify again. The error message continues to produce. 

#Trailhead Challenges