Python Django，无法接收paypal ipn通知

我正在尝试将django应用程序与paypal支付网关集成，但我没有收到信号，也无法接收paypal ipn通知

models.py views.py ti创建付款\u dic signals.py init.py 请注意，每当我重新加载本地服务器时，都会触发信号，

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所以你知道我的错误吗，谢谢。

最后我发现了我的错误，在我看来，这只是一个打字错误。py

views.py

class Pr_request(models.Model):
    number = models.CharField(max_length=20)
    subject = models.TextField(max_length=500)
    date_posted = models.DateTimeField(auto_now_add=True)

class Purchase(models.Model):
    resourse = models.ForeignKey(Pr_request, related_name='purchase')
    purchaser = models.ForeignKey(User)
    purchased_at = models.DateTimeField(auto_now_add=True)

def payment_proccess(request, id):
    pr = get_object_or_404(Pr_request, id=id)
    host = request.get_host()

    paypal_dict = {

    'business': settings.PAYPAL_RECEIVER_EMAIL,
    'amount': '%.2f' % pr.fees.quantize(Decimal('.01')),
    'item_name': 'purchase Req {}'.format(pr.number),
    'invoice': '2',
    'currency_code': 'USD',
    'notifiy_url'  : 'http://da...879.ngrok.io',#also i tried 
     localhost
    'return_url'   : 'http://{}{}'.format(host, reverse('payment:done')),
    'cancel_return': 'http://{}{}'.format(host, reverse('payment:canceled')),
    }

    form = PayPalPaymentsForm(initial=paypal_dict)
    print (" iam pyament process function")
    return render(request, 'payment/process.html', {'pr':pr, 'form':form})

def payment_notification(request, sender, **kwargs):
    ipn_obj = sender
    if ipn_obj.payment_status == ST_PP_COMPLETED:
        print ("successful payment was done Lol")
        pr = get_object_or_404(Pr_request, id=ipn_obj.invoice)
        pur = Purchase.objects.get_or_create(resourse=pr,
                                            purchaser=request.user,
                                            tx='some text')
        pur.save()
        #mark the pr as paid
    else:
        print (" not able to pay")
        # payment was successful

valid_ipn_received.connect(payment_notification)
print ("signal is fired")

default_app_config = 'payment.apps.PaymentConfig'

'notifiy_url'  : 'http://{}{}'.format(host, reverse('paypal-ipn')),
# should be changed to
'notify_url'  : 'http://{}{}'.format(host, reverse('paypal-ipn')),
# also here i have set the logged in user
'payer': request.user,