Use eBay Messages to ask the seller if he has received your payment.
There can be a disconnect between payment processors and eBay.
If you used a Debit card rather than a credit card, you were drawing from your bank account. In effect writing an e-check.
Just like a paper check, e-checks must clear the banking system before eBay will accept them as payment.
This delay is one reason it is better to use a credit card than a debit card.
Another is that it is much harder to get a refund on a debit card if things go pear-shaped.
