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

Hi! I was having that issue as well.  The way I fixed it was by labeling the Recent Items when I added it to the Lightning App Builder. The instructions don't say to do so but it is necessary.

Hopefully this helps!