Problems with embedded video in Interactive - Tabs Block

Hi,

I am new to Rise 360 and I am trying to use the Interactive - Tabs block to have 4 tabs each with an embedded video.

The video on Tab 1 works fine but the remaining 3 are all just showing blank iframe borders with no content at all.

Tab 1:

Tab 4:

If I paste the same iframe code into a single Multimedia - Embed block it works fine so it's not the embed code itself.

I am running via Edge Chromium with no access to any other browsers within the organisation.

Any ideas what I might be doing wrong here?  Thanks