Ok, so after some sleep!! I seem to have found the problem. The URL was wrong!! This was soooo simple, not Hype, not W3Schools, not even my members plugin etc.
I'll share my Diagnostics - in case this might be useful to anyone working in WordPress (or using Cyberduck and other FTP programs).
Daniel, thanks for your methodical and supportive videos. They are very calming!! Learning is certainly a spiral not a curve. I had used to that page before but earlier in my learning journey, though new things stood out on reviewing it. It is like a checklist for WP embedding if followed methodically.
I reviewed previous versions of my Hype doc where embed worked. (Luckily I had not deleted from the server and they still worked, so that was useful to know it was not some fundamental set-up problem)
Inspired by Hans' suggestion, I started a new clean, simple, single layout, single scene Hype doc but tried embedding it on my site (didn't work, good to know)
Drawn from Daniel's video, I noticed I was missing / ignoring a crucial step!! That is, pasting the hypegenerated....js file into the browser - to see if it's there.
Now here was the clue and the real problem. When I pasted the URL, WordPress would kick me out and redirect me back to my login page constantly! [ so I was looking at cookies, members plugin and all sort of unnecessaries....! ].
NOTE: I was thrown off the scent here because of my WP set-up(?), no 404 page or anything to say 'page/file not found' - just redirected back to login/front page.
I had also tried using an iframe and linking directly to the html and each time it would send me back to login (or front page, after disabling members plugin for a moment). It was appearing to me that I was not able to link to anything from my uploads folder.
Eventually I realised i was using THE WRONG URL missing 'wp-content/uploads...'. This is because I was using the URL copied from the ftp program (Cyberduck) I had not configured it properly so it was missing part of the URL. This meant I was using these dodgy URLs everywhere, including my pasted ' div...src="..." div ' code for the embed.
Now, while I am quite ashamed at my ignorance, I will reiterate that it would be nice if WP embeds from Hype were simpler. Using the ftp url was part of trying to simplify!! (ironically) By my frustration point I have been on such a journey with all this these last couple of weeks, just about to 'publish' and it didn't work!! I was so bogged down in ratioscale, screen sizes, and all sorts, I could not see this basic error! Not even w3 but www101!
Thanks again for your supportive responses, even if they amounted to, 'read the bl**dy docs!'
Now, a luta continua..
I have to work out why half my mouseovers no longer work. I'm sure it must be something symbol !