If your card is being declined every time you try to pay for a subscription or top up your balance, you don't need to keep retrying the same way — Easync can route your card payment through Paddle, an alternative payment processor, which usually clears cards that were failing before.
Message support in the chat and ask them to enable Paddle for card payments on your account; they select it on their side and confirm in the chat, and you can then complete the payment as normal.
If the card still won't go through even on Paddle, it's usually an issue on the card/bank side (for example, international transactions being blocked), so it's worth trying a different card or contacting your bank. If you'd rather not use a card at all, tell support and they can point you to the other supported payment options.