You're taking about a UK business seller with over 700,000 sales and over 55,000 in the last year, with 99.4% positive feedback. In any cased, it would be a starnge scammer who refused to accept your payments!
If your payments have not succeded the problem is more likely to be at your end. In any case, I imagine that they have been moved on to eBay's managed payments scheme by now, which means you don't pay the seller, you pay eBay. So if you want to discuss your failed payments, contact eBay.
