You are using your own engine, maybe this is causing problems. But I also did that in the past, and managed to get it running. You have one other game published - is this one also based on your own engine?
What I would check: Is every resource included in your zip file (no external dependencies, no requests to external domains)? Do you provide an index.html file? Is everything loaded and executed by requesting that file (opening it directly from a local file path and not via localhost webserver might be a good check)? Think your index.html must not contain any more iframes. These are the points I would check - good luck.