When I run this step in my Developer Org it works correctly, unfortunatley Trailhead won't verify this challenge and produces the following error

"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: DEMSOPHW"

This is preventing me from completing this Project (and receing a new Badge!!)

Hi!
I'm making a trail's project "Create a satisfaction Survey". 
When i wished  verify my trail , i received this error

I made other project and never i saw this error! Please, could i have some help ?