We can't marry players. It says that we must do /marry marry player1 player2 but it doesn't work.

Could you explain to me how to marry players ?

Are you using a priest or are you trying to marry on your own?

On my own, and I'm a priest and it doesn't work

You can only marry on your own if the option "Marriage.RequirePriest" is set to false. However then everyone would be able to marry on their own. Even if you are a priest you cannot marry yourself with an other player, unless the option is disabled.

If I do /marry marry TheIntelloBox player2 with "Marriage.RequirePriest" set to false, it says "you don't have permission to do that".