Can't get command reward to work

I am trying to allow users to execute a command when they have earned enough RP. For instance i want the player to be able to enter a "lotto" group that i have made. So i first made the group "Lotto" i then used the following code to add the command option to the rewards UI:

rewards add command "lotto" "oxide.usergroup add user $ lotto" 20

but when i pull the UI and go to commands it just shows  "--" for the name when it should show "lotto". also when i purchase it, it executes and my RP is taken away but im not added to the "lotto" group. anyone have any idea what im doing wrong? 


oxide.usergroup add $ lotto <--- This will add a user to the group lotto

/rewards add command <name> <command> <cost>
/rewards add command lotto "oxide.usergroup add $ lotto" 20 <--- This should work for what your looking for