> oxide.rant group default skipnightui.admin
permission 'skipnightui.admin' doesn't exist

so i tried another

>oxide.grant user (myID) skipnightui.admin
Permission 'Skipnightui.admin' doesn't exist

Did i type something wrong or? its not working for some reason

the plug is installed in the correct Oxide folder as well

The only way you'd see that message is if the plugin is not loaded. Please check your oxide/logs for errors and make sure you have any depedencies loaded.