Having trouble getting custom headers to work

Hi, it seems like I have everything correct, but as you can see, the x-frame-options header is not appearing, for example.

https://greatmates.pages.dev/
https://mm.global
account id: 7db2928ba7c67dfcf1784ad36892e88d
zone id: 2b9a750c3bd92af81f8d68db2567ad1a