Videos Tutorials not accessible in Zendesk

We use Zendesk for our client support/helpdesk, and we've set up a Tips & Tricks section there for text and video FAQs. We have been posting the premium video tutorials there, and they had been working fine. Our subdomain is, and we listed it in our registered domains for displaying the videos.

Some time recently, the videos stopped working, and now they show an error. See attached screenshot.

What do we need to do to have the videos display as before?

Thanks for your help.