Saves to Users table shiphero refresh token but not access token

Hello, I have one issue with shiphero graphql api. When I submit shiphero credentials, it saves to users table shiphero refresh token but not access token, although looking below in code methods apart small differences are the same. I try pass or get refresh_token in numerous ways but with no avail. ShipherroWrapperGraphQL.php

class ShipheroWrapperGraphQL
{
    const AUTHENTICATION_URL = 'https://public-api.shiphero.com/auth/token';

    const AUTHENTICATION_URL_REFRESH = 'https://public-api.shiphero.com/auth/refresh';

    const REQUEST_URL = 'https://public-api.shiphero.com/graphql';

    protected $client;

    protected $user;
 public function __construct(User $user)
    {
        $this->client = new Client();
        $this->user = $user;
    }
public function getAccessToken($refresh_token)
    {

        Log::info('[Shiphero GrapQL] Requesting Access Token');

        try {
            $response = $this->client->request(
                'POST',
                self::AUTHENTICATION_URL_REFRESH,
                [
                    RequestOptions::JSON => [
                         'refresh_token' => $refresh_token,
                    ]
                ]
            );
        } catch (\Exception $e) {
            Log::error('[Shiphero GraphQL] Access Token Error ' . $e->getMessage());
            return null;
        }

        if (empty($response)) {
            return null;
        }

        $responseContent = $response->getBody()->getContents();

        if (empty($responseContent)) {
            return null;
        }

        $decoded = \GuzzleHttp\json_decode($responseContent, true);

        $this->user->shiphero_access_token = Arr::get($decoded, 'access_token');

        $this->user->shiphero_access_token = $decoded['access_token'];

        $this->user->save();

        return $decoded['access_token'] ?: null;
    }

     public function getRefreshToken($email, $password)
    {

        Log::info('[Shiphero GraphQL] Requesting Refresh token');

        try{
            $response = $this->client->request(
                'POST',
                 self::AUTHENTICATION_URL,
                [
                    RequestOptions::JSON => [
                        'username' => $email,
                        'password' => $password
                    ]
                ]
            );
        } catch(\Exception $e){
            Log::error('[Shiphero GraphQL] Refresh Token Error '. $e->getMessage());
            return null;
        }
        if(empty($response)){
            return null;
        }
        $responseContent = $response->getBody()->getContents();
        if(empty($responseContent)){
            return null;
        }

        $decoded = \GuzzleHttp\json_decode($responseContent, true);

        $this->user->shiphero_refresh_token = Arr::get($decoded, 'refresh_token');

        $this->user->save();

        return $decoded['refresh_token'] ?: null;

    }
}

HomeController.php

  public function updateUser(EditUserRequest $request)
    {

        if(empty($request)){
            return redirect('home');
	}

        $user = User::find(Auth::user()->id);


        if(!empty($request->only('shiphero_email', 'shiphero_password'))){

            $shiphero_user = new ShipheroWrapperGraphQL($user);

            $shiphero_user->getRefreshToken($request->shiphero_email, $request->shiphero_password);

            $shiphero_user->getAccessToken(Auth::user()->shiphero_refresh_token);

        }

        if(!empty($request->password)) {

            $user->password = Hash::make($request->password);
        }