BigCommerce oAuth auth token request always returning 401 - oauth

Question

I can not figure out what I'm doing wrong. I'm developing an App for BigCommerce and can not get the simple oAuth exchange to work correctly.
The initial get request is being made to https://www.my-app.com/oauth/bigcommerce/auth. This is the code in the controller for that request. It's a Laravel 5.6 app:
use Illuminate\Http\Request;
use Bigcommerce\Api\Client as Bigcommerce;
class BigcommerceOAuthController extends Controller
{
public function auth(Request $request)
{
$object = new \stdClass();
$object->client_id = 'my-client-id';
$object->client_secret = 'my-client-secret';
$object->redirect_uri = 'https://my-app.com/oauth/bigcommerce/auth';
$object->code = $request->get('code');
$object->context = $request->get('context');
$object->scope = $request->get('scope');
$authTokenResponse = Bigcommerce::getAuthToken($object);
$storeHash = str_replace('stores/', '', $request->get('context'));
Bigcommerce::configure(array(
'client_id' => 'my-client-id',
'auth_token' => $authTokenResponse->access_token,
'store_hash' => $storeHash
));
echo "<pre>";
print_r($authTokenResponse);
print_r(Bigcommerce::getTime());
echo "</pre>";
}
}
Every time I try to install my draft app from the BigCommerce control panel, I get an error because $authTokenResponse is not an object. When I debug further into the Bigcommerce\Api\Connection class, I can see that the response from the server is empty, and the status is a 401, which means "Unauthorized".
I can't figure out why I am getting this error. As far as I can see, I'm doing everything right. I've tried urlencoding the string retrieved from $request->get('scope'), since that string becomes unencoded by Laravel, but that didn't seem to help.
I am also confused how this is even supposed to work at all. In the BigCommerce docs, they show this example POST request, which uses application/x-www-form-urlencoded Content-Type and passes the request body as a url encoded string:
POST /oauth2/token HTTP/1.1 Host: login.bigcommerce.com Content-Type:
application/x-www-form-urlencoded Content-Length: 186
client_id={CLIENT_ID}&client_secret={CLIENT_SECRET}&code=qr6h3thvbvag2ffq&scope=store_v2_orders&grant_type=authorization_code&redirect_uri=https://app.example.com/oauth&context=stores/{STORE_HASH}
However, if you inspect what's going on in the Connection class, you can see that the Content-Type is being set to application/x-www-form-urlencoded as the docs say, but the request body is being passed in as a json string, not a url string. Shouldn't the request be a url encoded string as the docs suggest?

Answer 1

A couple of things here to check:
Do you have a public URL where you can receive the Auth Callback?
If so, did the store owner registered the app successfully? https://developer.bigcommerce.com/api/registration
When you have the client_id and secret_id. You should have all of the details needed to send a POST request to the BC Auth Token Service at https://login.bigcommerce.com/oauth2/token
The content uses URL encode Make sure to URL encode your content. Be careful of of the encoding of & and = signs when those are actually being used as separators.
More details can be found in this post:
Can BigCommerce Private Apps use OAuth