When your first payment to OpenRouter succeeded and a later one is refused, while your bank says the card is normal, the cause is usually not the card. Risk systems at the payment processor and at banks watch how often the same card pays the same merchant. A second charge soon after the first, especially for a different amount or from a different device or network, can trip a repeat-charge rule that the first charge did not. Some banks also limit how many top-ups to one merchant they allow in a day.
These rules usually relax with time. The most effective step is to wait about 24 hours, then make one single one-time payment, not several attempts in a row. Every failed retry in the meantime adds to the pattern the filter is reacting to, and switching between cards from the same bank rarely helps, because the limit often applies per bank rather than per card. If you use a VPN, turn it off so the second payment looks like the first.
If it is still declined the next day, ask your bank whether it saw the attempt, and open a ticket with OpenRouter support noting that an earlier payment on the same card succeeded. If you need credits before then, a crypto payment does not go through the card processor at all: ROZO Checkout pays an OpenRouter payment link with BTC Lightning, USDC, USDT and more for a 1% fee, shown before you pay. ROZO is independent and not affiliated with OpenRouter or Coinbase.