I have been stalled in completing my WP site for three

I have been stalled in completing my WP site for three weeks. Just after checking out, instead of processing the order, it does not go to a Thank you page but back to the Billing Page with an error message about you must select a payment option. I have been posting for help numerous times without resolution. I am considering cancelling my subscription as no one will just look at this and offer real suggestions. I need help now. I have lost almost the entire Christmas selling season so you can understand my frustration.