Many thanks for your reply but I think there is a little miss-understanding of the issue.
The HTML loads in Edge, Chrome, etc just fine in EA v16 64 bit, (it does not load in EA v 15.2), the problem is that if a diagram has been selected in HTML generation dialog, then that diagram should be displayed when the HTML is loaded in the Browser. But no diagram is shown, the rest of the HTML displays just fine.
It appears that EA v 16 RC 64 bit always generates the same index.htm page completely ignoring the diagram settings on the HTML generation dialog.
Thanks for the powershell script, most useful
Phil