I have contacted Elementor support and here is the response from them.
“May I know where I can locate this issue?
The class names that you mention doesn’t seem to be related to our widget in any way. I would also like to know which widget of elementor you use here? Does this work if you don’t use it on an elementor page?
The screenshots don’t appear to be anything related to an elementor widget.”
I don’t think it’s an Elementor issue, either. I think it’s something wrong with the video unit code itself.
I’m not seeing anything theme (or Elementor) related which is hiding the unit on mobile. If the ad network sees different, I’m definitely happy to investigate, but they’d have to show me exactly what I’m looking for, as right now I’m not seeing anything.