i am using sandbox environment in paypal sdk integration and getting the following error anyone came across the error??

request failure with http statusCode:422,exception:org.apache.http.client.HttpResponseException: Unprocessable Entity

paypal.sdk﹕ request failed with server response:{"name":"PAYMENT\_CREATION\_ERROR","debug\_id":"968064d634e8e","message":"checkout-session not created","information\_link":"<https://api-m.sandbox.paypal.com/docs/api/#PAYMENT_CREATION_ERROR>"}

/paypal.sdk﹕ PAYMENT\_CREATION\_ERROR

here's my code

```
private static final int REQUEST_PAYPAL_PAYMENT = 1;
private static final int REQUEST_CODE_FUTURE_PAYMENT = 2;
private static final String CONFIG_CLIENT_ID = "id";

private static PayPalConfiguration config = new PayPalConfiguration()
        .environment(PayPalConfiguration.ENVIRONMENT_SANDBOX)
        .acceptCreditCards(true)
        .clientId(CONFIG_CLIENT_ID);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_read);
    Intent intent = new Intent(Read.this, PayPalService.class);
    intent.putExtra(PayPalService.EXTRA_PAYPAL_CONFIGURATION,config);
  b1 = (Button) findViewById(R.id.button);
    startService(intent);
 b1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
    PayPalPayment thingToBuy = new PayPalPayment(new BigDecimal(1),"USD", "androidhub4you.com",
            PayPalPayment.PAYMENT_INTENT_SALE);

    Intent intent = new Intent(Read.this, PaymentActivity.class);
    intent.putExtra(PayPalService.EXTRA_PAYPAL_CONFIGURATION, config);

    intent.putExtra(PaymentActivity.EXTRA_PAYMENT, thingToBuy);

    startActivityForResult(intent, REQUEST_PAYPAL_PAYMENT);
  }
 });

  }

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_read, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_PAYPAL_PAYMENT) {
        if (resultCode == Activity.RESULT_OK) {
            PaymentConfirmation confirm = data
                    .getParcelableExtra(PaymentActivity.EXTRA_RESULT_CONFIRMATION);
            if (confirm != null) {
                try {
                    System.out.println("Responseeee"+confirm);
                    Log.i("paymentExample", confirm.toJSONObject().toString());

                    JSONObject jsonObj=new JSONObject(confirm.toJSONObject().toString());

                    String paymentId=jsonObj.getJSONObject("response").getString("id");
                    System.out.println("payment id:-=="+paymentId);
                    Toast.makeText(getApplicationContext(), paymentId, Toast.LENGTH_LONG).show();

                } catch (JSONException e) {
                    Log.e("paymentExample", "an extremely unlikely failure occurred: ", e);
                }
            }
        } else if (resultCode == Activity.RESULT_CANCELED) {
            Log.i("paymentExample", "The user canceled.");
        } else if (resultCode == PaymentActivity.RESULT_EXTRAS_INVALID) {
            Log.i("paymentExample", "An invalid Payment was submitted. Please see the docs.");
        }
    }

}
@Override
public void onDestroy() {
    stopService(new Intent(Read.this, PayPalService.class));
    super.onDestroy();

}

```