If you have games on itch.io that are using resources hosted elsewhere you might have to fix them.
In my case that meant fonts I used from google’s CDN (fonts.google.com) suddenly stopped working.
Package all your assets (images, fonts, sounds) into the zip file that you upload, and use relative links to refer to everything.
(I think that’s good policy in any case. Google sometimes kills off services. Nobody thinks they’re going to kill off fonts.google.com, but who knows for sure…)
It’s possible that Itch will modify this policy if it causes widespread problems. Keep an eye on their discussion.