I'm trying to request a SM64 rom hack and after filling out the application I'm getting an error that says "You must have email authentication enabled to submit a Game Request." Can anybody tell me how to resolve this?

Settings > Account & Security > Email Authentication (2FA) > Enable two-factor authentication > On > Save

SM64 rom hacks have a separate review process than other games. You don’t have to fill out the site’s request form. The last post here has instructions:

https://www.speedrun.com/sm64romhacks/thread/m9y3r/7