Why does Discord refuse to embed my website?

My website embeds perfectly as expected everywhere I’ve tried except Discord, for some reason it refuses to embed no matter what I try and I cannot figure out why, I’ve tried:

  • remaking my tags entirely;
  • stripping my backend of all security;
  • completely rebuilding my backend; and
  • allowing Discord through every bit of security I have.

The only times it has embedded properly were when I tried hosting one of my html files on tiiny.host and on GitHub Pages, so it must be something in my backend, but the only things I could think of possibly causing it were CORS, CSP, and Helmet, but even removing all 3 of them entirely didn’t work.