Steps to reproduce: 

1. Create new world, have the "activate cheats" toggle off when setting it up (set it up so it's possible to get xbox live achievements), enter world as you normally would to create it, then leave the world.
2. Create a copy of the world via the world settings menu, don't enter it yet. 
3. In the world copy settings menu, change gamemode to creative using the default game mode dropdown in the menu
4. Enter the world copy
5. Try to use a cheat command like /locate, /tp, /time set, /gamemode, etc., it will not let you do so, instead giving you "Unknown command: [blah blah blah]. Please check that the command exists and that you have permission to use it."

What went wrong?

Commands that usually work when cheats are turned on don't work with cheats turned on. When you toggle gamemode via the menu while in the game (but not out of the game in the world settings menu on world select), it does seem to kickstart the permissions and allow you to use cheats on that world.

TL;DR: When you make a copy of a world with cheats off, the cheats off carry into the copy even if cheats are on in the copy. Minor annoyance.