I got an error on the payment screen
Your invitation is not lost; it stays as a draft. You can try again from your dashboard. Card details are never stored anywhere on our side.
My card was charged but the invitation was not published
This is usually a pre-authorization held by the bank and it clears by itself. Still, open a support request and write these three things: the time of the transaction, the last four digits of the card, and the name of the invitation. Attaching a screenshot moves it along much faster.
I paid twice
An invitation is never renewed by a second payment. We refund the second one; opening a request is enough.
Invoice
You can reach your invoice details from the payment history screen.