Sound Loss & File Size on Video Pages

Site URL: https://www.flowerchildheirloom.com

I am trying to upload a video to a video page and it meets all the requirements but it doesn’t play the sound?

I have tried different formats and sizes and nothing.

Also, I use iMovie to edit my videos.  What is the best size to maximise quality?

 Thank you 

Can you point us to a page with a video on it so we do diagnostics?

It’s password protected at the moment as it’s a paid for course.