...ok one last try, I think I know what you are saying. You are using the unified post form and you are embedding videos with embed.ly through froala in the video post form on the timeline. If so, on my end there is no thumbnail, because I just embedded the video without uploading a photo, but the video shows up on the videos homepage and when I click on the video it plays on the view videos page. If that is what is going on and you can't see the video on the view videos page, then there is an issue. If needed, you can remove the video embed link in studio: Froala>settings> by removing "embedly" from the toolbar buttons, but the issue still won't be solved.

There should be a feature that automatically turns video links and embedded videos into playable videos just by pasting the link in the text area of any form.