Hi there,
Does your project not play at all or does it not play only the inserted video?
What kind of video is it? Is it an event Video or multi slide synchronized?
Make sure that there is no unsupported object for HTML 5 in your project, please check this artilce: http://helpx.adobe.com/captivate/using/publish-projects-html5-files.ht ml
Have you tried to publlish with only HTML 5 option checked?
Thanks.