Fix order retry issue

src/pretix/presale/templates/pretixpresale/event/order_pay.html

@@ -11,6 +11,7 @@
 
     <form method="post" class="form-horizontal" href="" data-total="{{ order.total|floatformat:2 }}">
         {% csrf_token %}
+        <input type="hidden" name="payment" value="{{ provider.identifier }}">
         <div class="form-horizontal payment-redo-form">
             {{ form }}
         </div>

src/pretix/presale/views/order.py

@@ -172,6 +172,7 @@ class OrderPaymentStart(EventViewMixin, OrderDetailMixin, TemplateView):
         ctx = super().get_context_data(**kwargs)
         ctx['order'] = self.order
         ctx['form'] = self.form
+        ctx['provider'] = self.payment_provider
         return ctx
 
     @cached_property