Why is Call to a member function roles() on null?

Question

Laravel

Did the code
Auth::user()->roles()->attach(Role::ID__CUSTOMER);
return in the logs where could it find null there? Authorized user. The relation manytomany to roles is used everywhere, the role with the specified id exists. What can be checked?
Call to a member function roles() on null

Answer 1

The response from the service is not an authorized user.
So

$user = User::find($user_id);
$user->roles()->attach(Role::ID__CUSTOMER);