Hello, i am walking thourgh the Trailhead sessions and got this error message after checking on a challenge. Can you help me how to continue? THX! 

Challenge Not yet complete... here's what's wrong:  There was an unexpected error while verifying this challenge. Usually, this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: AZUNUJEN

Hello, i am walking thourgh the Trailhead sessions and got this error message after checking on a challenge. Can you help me how to continue? THX! 

Challenge Not yet complete... here's what's wrong:  There was an unexpected error while verifying this challenge. Usually, this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: AZUNUJEN