If checkout works on mobile but not desktop, compare the same cart and checkout stage at about the same time. Note whether the devices use the same network and payment method; changing several variables at once makes the result harder to interpret. Record a safe error code and whether the failure occurs before or after payment submission.
Do not post card data, billing address, account identifiers, or order links. Check order history before any retry, especially if the desktop page timed out after Pay. A browser extension, stale session, network route, or partial incident could explain the difference, but the comparison alone does not prove which. Report the exact observed difference to official support.
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