If you can't find a specific test to create, please first make sure it's public or scheduled and then hit the "Update All Video Data" button.
If that doesn't work, then please follow these steps:
Go to team settings https://app.thumbnailtest.com/settings/team
Scroll down to the channels table
Click on the "Manage" button under missing videos in the row of the channel that is missing the videos
Put the videoID or video URL of the missing video in the input box
Click submit
Then go to the "New Test" page https://app.thumbnailtest.com
Click on the "Update All Video Data" button
Then try searching for one of the missing videos
Repeat steps 4 & 5 if you have more than one.
What causes this?
Due to the way we fetch the list of the channel's uploaded videos, it unfortunately has a known long-lasting Youtube API bug that may not return all of your videos.