Regarding error while verification step in Create Validation Rules

Hello Trailhead Support Team,

I am currently working on the Trailhead project "Customize a Salesforce Object" and am stuck on the final step, "Create Validation Rules."

I have completed the required tasks as instructed:

• Created the Account validation rule: Support_plan_expiration_date_required
• Created the Opportunity validation rule: Close_reason_required_when_lost
• Activated both validation rules
• Verified the formulas, error messages, and error locations match the challenge requirements
• Saved all changes successfully

However, when I click "Check Challenge," I receive the following error:

"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 have already refreshed the Playground, retried the verification multiple times, and confirmed there are no additional Opportunity validation rules.

Could you please review my Playground and help resolve this verification issue?

Playground Name: Curious Koala Playground

Thank you for your assistance.

Kind regards, 

Keerthana D P