iframe code trick - is there a way to render storyline html (or converted to aspx) output in Sharepoint preventing it downloading instead

I've tried every html conversion to aspx trick, nothing works.  Each time I either link to or embed an html storyline output (in an open folder in sharepoint online) it downloads it rather than opening it in a browser tab or in-page iframe.  I have reviewed many posts here, no method works.  It makes no difference if the callee is modified from html to aspx.  Any ideas?