Just to chime in a little:
This is likely because the call isn’t preceded with calling the parent; @MaxZieb has the later example that works in an HTML Widget (iframe):
But if you are not in an iframe but instead say the Inner HTML of a Rectangle, then HYPE is in the current window (and not the parent), so you’d use:
But the other thing I really wanted to mention is that “index” in this case is always used for Preview, but at export the document name is based on the name used for the export, and so will likely be different unless you called your export “index”. So just note you may have to change this before going live.