You can resolve many intermittent video playback issues on your Kindle Fire Tablet by clearing application data.
- Swipe down from the top of your screen, and then tap More or Settings.
- Tap Applications, and then Installed Applications.
- Select All Applications from the drop-down menu and then open Quickflix.
- Tap Force stop, and then tap Clear Data.
After you've cleared your video app data, restart your device and try playing the video again.