Why can't I use the /locate biome command?

My sister created a Realm and made me an Admin/Operator. However, whenever I attempt to use the command, I get "Incorrect permission level for command: locate". This happens with other commands.

I have had my sister

1. Remove permissions and re-add them, to which I relogged

2. Remove me completely from the Realm, re-add me, and re-grant permissions

I have also logged into her account to do the same. I'm losing my mind here. What do I do?