No such plan: monthly; one exists with a name of monthly, but its ID is primary Laravel Cashier

Getting this problem in Stripe test. Everything used to work in test, but when I created a new plan in Stripe, and deleted the original one, I now get the following error:

No such plan: monthly; one exists with a name of monthly, but its ID is primary.

Controller

$user->newSubscription('primary', 'monthly')->create($token, [ ]);

Plan details

ID: primary
Name: monthly
Price: $19.99 USD/month
Trial period: No trial

php artisan config:clear doesn't help. I'm using Laravel 5.2 and Cashier 6.0.

.env file

STRIPE_KEY=pk_test_...
STRIPE_SECRET=sk_test_....

config/services.php

'stripe' => [
    'model'  => App\User::class,
    'key'    => env('STRIPE_KEY'),
    'secret' => env('STRIPE_SECRET'),
],

via Chebli Mohamed