Your uploaded and embedded FLV videos, when they are not set to autoplay AND you have auto-hide controls, will always show the very first frame of the video in its placeholder.
Here's what you can try to fix this:
- Set the video to autoplay so as soon as the page is loaded the user will see the video playing
- Uncheck AutoHide Controls so the user will see video controls and recognize the object is a video that needs to be played
- Edit your video so the very first frame is a still image from the video itself. Choose a still image that well represents that video and perhaps put a PLAY button overlaying that image so end users know it is a video.