Cashier Laravel error on create new Subscription

I'm trying to implements laravel cashier in my project. I have laravel 5.5 and cashier 7.2.2.

I have a problem when I try to createNewSubscription.

In my controller I have:

$user = User::find(3);
$subscription = $user->newSubscription('Base', 'price_45asd456a1sa56sd4');
$subscription->create($token);

But I receive this error:

"Call to a member function create() on null" on line 415 of /var/www/html/vendor/laravel/cashier/src/Billable.php

The problem is that in trait return error in:

$card = $customer->sources->create(['source' => $token]);

Because $customer->sources is null. But why?

I can see that in my db the stripe_id is setted, and in dashboard of stripe the Customer is created.

via Chebli Mohamed