In normal worlds the ranks do appear, in realms or servers even if you have the beta option activated the ranks option does not appear, you should take a look at it.
This seems cool and I like the textures! But I already have a Ranks mod on my server and I would be cool If you could make a resource pack without the technical stuff that I could use with that mod. This is great though, keep up the good work!
Make sure your version is 1.21.100/1.21.101 and double check if the tag is correct, this should be "admin", and the experimental you should enable is BetaAPIs.
After that try to use /admin:ranks and see if the menu is working
/tag @s add admin
And the tag must be lowercase
(Sorry for my bad English)
After that try to use /admin:ranks and see if the menu is working
Try to use this command: /ranks