The Leash Ring gives me the error: "Sorry, but you are no longer authorized to do that"

Only your pet's registered owner is able to use the Leash Ring to do things like force-tp her. If  you have been temporarily or inadvertently removed, you can get your pet to set you as owner again by following these instructions.

If you are your pet's registered owner, then there could be a sync issue. You can ask your pet to reset her HUD (ask her to say "/1.reset" where /1 is her command channel). If that doesn't work, ask her to set you again as owner.