Custom "business" logic using pure Django - django

Question

I am set on building a small website using django. What i am trying to do right now is using a CreateView based on a Model "Order", which one of its fields is another model "Customer".
The form itself works to create Orders, but im trying to find out how i can validate that the Customer that was selected is "enabled" (there is a status in the Customer model).
I was trying using the clean method but it doesnt even seem to be executing. I tried just raising the error on the clean, without validating anything, and still doesnt work. Any clue what might be wrong?
My Form:
class OrderForm(ModelForm):
def clean_customer(self, *args, **kwargs):
raise forms.ValidationError("This customer is banned.")
class Meta:
model = Order
fields = '__all__'
Relevant Models:
class Order(models.Model):
ORDER_STATUS = (('Pending Delivery', 'Pending Delivery'),
('Book on Customer', 'Book on Customer'),
('Overdue', 'Overdue'),
('Completed','Completed'))
customer = models.ForeignKey(Customer, null=True, on_delete=models.SET_NULL)
book = models.ForeignKey(Book, null=True, on_delete=models.SET_NULL)
date_created = models.DateTimeField(auto_now_add=True)
date_due = models.DateTimeField(null=True)
date_completed = models.DateTimeField(null=True, blank=True)
status = models.CharField(max_length=100, choices=ORDER_STATUS, null=True)
def get_absolute_url(self):
return reverse('orders')
class Customer(models.Model):
status = models.CharField(max_length=10, null = True, choices=STATUS_CHOICES)
name = models.CharField(max_length=200, null=True)
username = models.CharField(max_length=25, null = True)
email = models.EmailField(null=True)
def __str__(self):
return str(self.name)+" - " +str(self.username)
def get_absolute_url(self):
return reverse('customers')
The View:
class OrderCreateView(CreateView):
model = Order
fields = '__all__'
def form_valid(self, form):
return super().form_valid(form)