According to the rules, the source code had to be available as a ZIP file or Tarball directly from the itch.io page. I think that's the reason, anyway. I'm not involved at all, but that looks like the most likely explanation.
Viewing post in Ummmm... Where's my submission?
OK... If that's the deal, then no problem. I have now attached harmony_source_latest.zip to my game page.
@mfiano, if this is the problem, can you please reinstate my entry?
If it's not, then please do let me know what's missing because as far as I can tell, I am otherwise completely in compliance with rules as stated. Thanks!