Storyline Firefox Issue

Good morning, 

I recently created a product overview tutorial for a client and the person committing it to their site sent this problematic message. Does anyone have any suggestions for how I can assist them? They have it uploaded and are trying to create a link so they can send it to prospects, apparently that link is not working all of the time. Could this be a publishing issue on my end? Pop-up blocker issue originating from Firefox?

I am quoting his email here:

"This flash video has cross reference between http and https. That cause security issue, so Firefox stop to load.

If you know who create this video, please make sure all reference should be relative."

I look forward to hearing your suggestions.

Thanks,

Magen