Hi there! I’m here to help you with the issue you’re facing while trying to complete your online order. I understand that it’s indicating there’s a problem with your payment method, even though you’re confident that’s not the case.

Let’s go through a few steps together to figure this out:

1. Check Payment Method: First, could you please double-check the payment method you’re trying to use? Make sure the card details, including the expiration date and security code, are entered correctly.

2. Billing Address: Sometimes, an issue can arise if the billing address doesn’t match what your bank or card issuer has on record. Could you confirm that the billing address you entered matches the one linked to your payment method?

3. Browser Issues: Since you're using a WebKit-based browser on Windows, it might help to clear the cache and cookies. This can often resolve issues related to online orders. Here’s how you can do that:
- Open your browser settings.
- Look for options related to privacy or security.
- Find the option to clear browsing data, and select cache and cookies.
- Restart your browser and try placing the order again.

4. Try a Different Browser or Device: Sometimes, switching to a different browser can help. If you have another browser installed, or even another device, please give that a try.

5. Contacting Support: If you've checked all of the above and the issue persists, it might be best to contact M&S customer support directly for further assistance. You can reach them at this link if you need personal support about your order.

Would you like to tackle any of these suggestions together, or do you need any further specifics on how to proceed? 😊