Review 360 doesn't play audio on mobile devices

I have several projects on Review 360. Stakeholders are able to watch and listen from computers and tablets, but when they try on a phone the audio does not come through. It is every project, but here is one example. I know some have iPhones, I am not sure if it is only iPhone. 

https://360.articulate.com/review/content/9430e7cc-c9c0-4a4f-ac8c-2f2e2560ef2b/review