This happened to me twice. One item I just gave up on. Another item (a speedy 35 Azur) I did the same as you calling, checking my credit card, my email, my account. Anything the CS could guess at that was my fault. It didn't matter that I had used the account many times, same email, same address, same credit card the CS would not accept that it could possibly be on their end.
After attempting to purchase approximately 15 times over the course of a few days I got irritated and I clicked "use PayPal". This was not how I wanted to pay. But I clicked it. I must not have been signed in and the order went through instantly creating a new account in my husbands name. Our joint PayPal account was set up in his name and email. It went through, set up a LV account for him and never canceled.
Shortly after a tPFer said I might have been blocked from purchasing the canvas piece if I had purchased too many canvas pieces prior. Sure enough I had recently bought maybe 4-5 canvas pieces. So maybe that was it.???? I'm tired of these games.