sandbox: "we're sorry,Things don’t appear to be working at the moment"

[GiuTom]

environment : sandbox

I use react native, and followed document of express checkout,tested under sandbox

when I was invoking 

public void setupBraintreeAndStartExpressCheckout(String amount) {
        try {
            PayPalRequest request = new PayPalRequest("1.00");
            request.currencyCode("USD");
            request.intent(PayPalRequest.INTENT_AUTHORIZE);
            PayPal.requestOneTimePayment(mBraintreeFragment, request);
        }catch (Exception e){
            onError(e);
        }
    }

then jump to website, and login with a sandbox account, after a longtime loading, failed

and got message "we're sorry,Things don’t appear to be working at the moment" 

please help me!

here is my code

public class PaypalCheckout extends ReactContextBaseJavaModule implements PaymentMethodNonceCreatedListener, BraintreeErrorListener{
    public static BraintreeFragment mBraintreeFragment;
    private ReactContext context;
    @Override
    public String getName() {
        return "PaypalCheckout";
    }

    public PaypalCheckout(ReactApplicationContext reactContext) {
        super(reactContext);
        this.context = reactContext;
    }

    private void sendEvent(ReactContext reactContext,
                           String eventName,
                           @Nullable WritableMap params) {
        reactContext
                .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
                .emit(eventName, params);
    }

    @ReactMethod
    protected void onClientTokenFetched(String clientToken,Promise promise) {
        try {
            mBraintreeFragment = BraintreeFragment.newInstance(this.getCurrentActivity(), clientToken);
            promise.resolve(true);
        } catch (InvalidArgumentException e) {
            onError(e);
            promise.reject(e);
        }
    }

    @Override
    public void onPaymentMethodNonceCreated(PaymentMethodNonce paymentMethodNonce) {
        // Send nonce to server
        String nonce = paymentMethodNonce.getNonce();
        WritableMap params = Arguments.createMap();
        params.putString("nonce",nonce);
        sendEvent(getReactApplicationContext(),"onPaypalGetNonce",params);
        if (paymentMethodNonce instanceof PayPalAccountNonce) {
            PayPalAccountNonce payPalAccountNonce = (PayPalAccountNonce)paymentMethodNonce;

            // Access additional information
            String email = payPalAccountNonce.getEmail();
            String firstName = payPalAccountNonce.getFirstName();
            String lastName = payPalAccountNonce.getLastName();
            String phone = payPalAccountNonce.getPhone();

            // See PostalAddress.java for details
            PostalAddress billingAddress = payPalAccountNonce.getBillingAddress();
            PostalAddress shippingAddress = payPalAccountNonce.getShippingAddress();
        }
    }

//    @Override
    public void onCancel(int requestCode) {

        WritableMap params = Arguments.createMap();
        params.putInt("code",requestCode);
        sendEvent(getReactApplicationContext(),"onPaypalCancel",params);
        // Use this to handle a canceled activity, if the given requestCode is important.
        // You may want to use this callback to hide loading indicators, and prepare your UI for input
    }

    @Override
    public void onError(Exception error) {
        if (error instanceof ErrorWithResponse) {
            ErrorWithResponse errorWithResponse = (ErrorWithResponse) error;
            BraintreeError cardErrors = errorWithResponse.errorFor("creditCard");
            WritableMap params = Arguments.createMap();
            params.putString("error",errorWithResponse.getMessage());
            sendEvent(getReactApplicationContext(),"onPaypalError",params);
            if (cardErrors != null) {
                // There is an issue with the credit card.
                BraintreeError expirationMonthError = cardErrors.errorFor("expirationMonth");
                if (expirationMonthError != null) {
                    // There is an issue with the expiration month.
                }
            }
        }
    }

    @ReactMethod
    public void setupBraintreeAndStartExpressCheckout(String amount) {
        try {
            PayPalRequest request = new PayPalRequest("1.00");
            request.currencyCode("USD");
            request.intent(PayPalRequest.INTENT_AUTHORIZE);
            PayPal.requestOneTimePayment(mBraintreeFragment, request);
        }catch (Exception e){
            onError(e);
        }
    }
}

[CoLeHP]

Hello GiuTom,
Have you found any solution? Unfortunately I have the same issue.