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.

Hi everyone, 

I am working on the "Create Validation Rules" challenge and facing this background error when clicking the verification button:  

"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." 

I have already created the validation rule 'Support_Plan_Expiration_Date_Required' on the Opportunity object. I also checked for picklist restrictions and field dependencies, but the background test data insertion is still failing.  

What other backend automations, flows, or duplicate rules on Account/Opportunity could be blocking this standard test data insertion?  

Any guidance would be highly appreciated. Thanks!