If you have correctly entered your card details and ensured that you have sufficient funds on your card, then here are some other solutions to consider:
Check card restrictions: ensure that your card supports online payments and international transactions. Contact your bank to remove any restrictions that may be affecting your card's usability for online transactions.
Check for account restrictions: some banks may impose restrictions on card transactions, such as limits on the number of transactions or a maximum amount for a single transaction. Contact your bank to check the limit.
Verify 3D secure authentication: if your bank uses 3D Secure technology for added security, make sure you follow the instructions on screen. Sometimes this will require you to enter a one-time password (OTP) received via SMS to confirm the payment. If needed, re-enter your card details to receive a new OTP or to re-try validating your payment through 3D Secure. If you have any questions about this process, contact your bank for assistance.
Contact bank support: reach out to your bank's support using the phone number on the back of your card or on your banking app. Inform them about the issue with the declined payment to your trading account and provide them with the date and amount of the declined transaction. They can provide specific reasons and assist in resolving the problem.
Try another card or payment method: if possible, you may want to attempt to deposit funds using a different card or payment method such as wire transfer, ApplePay, or other available options, as there may be issues specific to the first payment method you tried.
Note: avoid making multiple card deposit attempts within a short period (eg twice in 10 minutes) to protect your card from potential blocking due to security reasons.