Video Player for DT 8.9.6 not working

I am using DT 8.9.6 and am having trouble getting videos to play. When I add a video to a listing all I get is a small black box with a play arrow in it. Click the arrow and the box opens to larger size but no video will play. However, when I go to the listing manager and look at the attachments the video shows up as an attachment and will play from the manager page. The video is just an MP4 that I uploaded from my computer. Does anyone know what may be causing this sort of behavior?