Checking your log, we see this error (warnings are not errors, just warnings, of course it shouldn't be there but they don't do fail a php script):
[b]Fatal error: Maximum execution time of 30 seconds exceeded in classesHTML2WordML.inc on line 617[/b]
EmbedExternalHTML example downloads a whole page and transforms it to DOCX. So as it takes more than 30 seconds, you should increase your time limits in your php config.
Regards.