Paypal api – How do I get PayPal to work with Laravel PHP?

Seems like nobody in the last 5 years has tried to get PayPal to work with a Laravel site on PHP so I am forcibly asking now.
I am using this package: https://github.com/srmklive/laravel-paypal
And I am sending PayPal this:

array:6 [▼
  "items" => array:2 [▼
    0 => array:3 [▼
      "name" => "Product 1"
      "price" => 9.99
      "qty" => 1
    ]
    1 => array:3 [▼
      "name" => "Product 2"
      "price" => 4.99
      "qty" => 2
    ]
  ]
  "return_url" => "https://github.com/payment/success"
  "invoice_id" => "PAYPALDEMOAPP_1"
  "invoice_description" => "Order #PAYPALDEMOAPP_1 Invoice"
  "cancel_url" => "https://github.com/cart"
  "total" => 19.97
]

These values are purely for testing of course but they should work.
However, I get this error:

array:3 [▼
  "type" => "error"
  "message" => ""
  "paypal_link" => null
]

My code looks like this:

public function start()
    {
        $provider = new ExpressCheckout();

        $data = [];
        $data['items'] = [
            [
                'name'  => 'Product 1',
                'price' => 9.99,
                'qty'   => 1,
            ],
            [
                'name'  => 'Product 2',
                'price' => 4.99,
                'qty'   => 2,
            ],
        ];

        $data['return_url'] = 'https://github.com/payment/success';
        $data['invoice_id'] = 'PAYPALDEMOAPP_' . 1;
        $data['invoice_description'] = "Order #{$data['invoice_id']} Invoice";
        $data['cancel_url'] = 'https://github.com/cart';

//        $data['return_url'] = url('/payment/success');
//        $data['cancel_url'] = url('/cart');

        $total = 0;
        foreach($data['items'] as $item) {
            $total += $item['price'] * $item['qty'];
        }
        $data['total'] = $total;

        $response = $provider->setExpressCheckout($data);

        dd($response);

        return redirect($response['paypal_link']);
    }

These values are exactly the same as the one used by https://github.com/srmklive/laravel-paypal-demo/
Which is a working demo!
I looked into it further an found where the requests are sent within the package and it sends a POST Request to https://api-3t.sandbox.paypal.com/nvp and when I recreate the request with the same postdata in postman, I get ACK=Failure&L_ERRORCODE0=81002&L_SHORTMESSAGE0=Unspecified%20Method&L_LONGMESSAGE0=Method%20Specified%20is%20not%20Supported&L_SEVERITYCODE0=Error which is what I believe the real error to be.
If anyone could help, that’d be great!