After using /maptool explore command this message appears:

Same issue with these commands: /maptool get (map) /maptool delete (map). The only few commands that work are maptool new & maptool rename
Issuing maptool list causes error in console:

Just noticed "Cannot reproduce" tag.
Well, the issue is you're using in your api mojang's servers to fetch player's UUID, so, if there's no license account with such nickname, it fails to retrieve UUID, which is a big issue for online-mode=false servers.
If you use bukkit's methods to get UUID, everything works exactly as expected

Bukkit's methods are a bit more trickier than this. bukkit.getPlayer(UUID) only return player that is actually connected, else null
bukkit.getPlayer(UUID) return an Offlineplayer that connected once, lastly we try to retrieve from mojang the player UUID if no player is known. I didn't managed to replicate this, when I got time I will try with the offline mode. Thanks for the idea

This player doesn't exist. That's why this doesn't work. But I got one time the issue with the list. I'm still investigating the issue

So the plugin won't work on servers using online-mode false?

If the player is logged on your server that should work (if bukkit is able from a name to give an uuid) (I will check tonight if it's something missing or if it's an issue from bukkit.getofflineplayer that don't work with off-line server)

Okay, thanks! Waiting for your reply.

How is that possible? The command is being executed by player.

This player doesn't exist.

https://fr.namemc.com/search?q=Profo228 he doesn't exist for namemc too