User Roles Not Working But are already Set

i am using wp mu and i have added a user with role authur and i am is admin of this site..when i checked user role through the code by making plugin and putting in mu-plugins folder.. it shows error even for site admin.i.e

“you don’t have sufficient privileges.“

then i use this code..it again gives false answer for all users including admin..

user_roles i tried = (admin,editor,authur,etc)

if( in_array( "user_role", (array) $user->roles )){

}