If you ever notice a feature like this (video block not creating a thumbnail) not work properly, try clearing the Cache and Cookies in your browser. When you visit sites with your browser, your browser downloads and stores parts of those sites to prevent repetitive loading and to speed up the browsing experience. Although they can be helpful, Cache & Cookie data can also cause tiny issues like what you are experiencing to surface, so it's a good practice to clear them every once in a while.
If you haven't done this before, I’ve included instructions for Chrome, Safari, and Firefox. Simply click on the name of your browser and follow the instructions. Easy!
If after you've cleared the Cache & Cookie data you are still experiencing issues that you would like for use to troubleshoot further, give us a call at (888) 493-2525 and w're glad to help!