Hello NY13905
Welcome to the SBB Community.
What is the ticket about?
As a general saying, ticket sales start from six to two months before the departure date.
If it would be too early for the ticket purchase you would not even be able to choose a ticket at all.
It rather looks like your entered data is not OK. Please try entering all information in full capital letters AND, before sending proceeding, change the country selection (drop down) to another country and reset to the correct country.
Also, payments only work if your credit card were supporting the 3D secure ID security standards.
Let us know if it works now.
Kind regards,
Roland