I want to move the billing address form below the shipping address in the checkout, on the first page/step.
I created a custom module like tigren method https://www.tigren.com/billing-under-shipping-address-m2/
It all works fine, but when I press the place order button and want to complete the order I get the following error message:
"please check the billing address information. regionid is required."
So the billing address is not transferred, who can help me?