The payment window expired and my payment is stuck
Each invoice has a 30-minute payment window. If your transfer arrived later, or the network took longer to confirm it, the invoice closes — and the payment page may show the payment as cancelled even though the money is on its way or has arrived.
What to do
don't pay again; find the TXID and check the status in a block explorer. If the transfer is confirmed and reached the invoice address, contact the store with the TXID and your order number — they'll see the payment and decide whether to fulfil the order or refund you. If the transfer is still pending, the network is busy: wait for confirmation, then contact the store.