Problem with Video Playing in Browsers

Hi, we are having a problem with viewers saying they cannot watch the videos using Firefox on a Mac. The link is iaabcjournal.org (and it happens with any of the blogs listed, such as https://iaabcjournal.org/2016/06/17/case-study-linda-and-joe/ or https://iaabcjournal.org/2016/06/17/behavior-consulting-and-declawed-cats/.

I had someone recommend that we have videos saved in both the versions we have (mp4 or wmv) and also .webm and .ogv(.ogg). I assume this means we would have to have more than one instance of the video on the page? Or is there another issue preventing the videos from playing in Firefox?

Thank you!

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