Laravel Cashier using Stripe - No API key provided. Set your API key when constructing the StripeClient instance

Question

I seem to be getting the following error when I run $user->createSetupIntent()

No API key provided. Set your API key when constructing the StripeClient instance, or provide it on a per-request basis using the `api_key` key in the $opts argument.

I have added Billable to my User model

use Laravel\Cashier\Billable;

class User extends Authenticatable
{
    use Billable;
    use Notifiable;
    use SoftDeletes;
    use HasFactory;

And have added both my STRIPE_KEY and STRIPE_SECRET to my .env file.

I have also added to my services.php file

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

This was working earlier today but for some reason seems to be failing now. If I run ddd(\Stripe\Stripe::getApiKey()); the API key is returned correctly. However, if I go to the BaseStripeClient.php in the Vendor directory and add ddd($this->config) to the getApiKey method I get the following returned.

"api_key" => null
"client_id" => null
"stripe_account" => null

I have also tried following other solutions such as setting the api key in the register function.

    public function register()
    {
        Stripe::setApiKey(config('services.stripe.secret'));
    }

And tried in the boot function

    public function boot()
    {
        Stripe::setApiKey(config('services.stripe.secret'));
    }

Has anyone else come across this issue before? Why is my api_key not set in the stripe vendor files and how can I get it set?

Update

After looking in the Stripe BaseStripeClient.php file I found that commenting out the new error allowed me to successfully add a payment, which pulled through to Stripe.

private function apiKeyForRequest($opts)
{
    $apiKey = $opts->apiKey ?: $this->getApiKey();

    if (null === $apiKey) {
        $msg = 'No API key provided. Set your API key when constructing the '
            . 'StripeClient instance, or provide it on a per-request basis '
            . 'using the `api_key` key in the $opts argument.';

//        throw new \Stripe\Exception\AuthenticationException($msg);
    }

    return $apiKey;
}

I have also tried adding the api key via the Cashier class in the boot function

Cashier::stripe(['api_key' => 'sk_test_***']);

If I then open the Cashier file in the vendor directory and ddd the result

public static function stripe(array $options = [])
{
    ddd(new StripeClient(array_merge([
        'api_key' => $options['api_key'] ?? config('cashier.secret'),
        'stripe_version' => static::STRIPE_VERSION,
        'api_base' => static::$apiBaseUrl,
    ], $options)));
    return new StripeClient(array_merge([
        'api_key' => $options['api_key'] ?? config('cashier.secret'),
        'stripe_version' => static::STRIPE_VERSION,
        'api_base' => static::$apiBaseUrl,
    ], $options));
}

Then I get the correct api key value returned. However when I comment this out and simply return the new StripeClient, I get null again. How is it that the results are different when I'm essentially running the same code? So I'm really not sure how to correct this