The most common reason a transaction is declined is because the billing address provided doesn't match what your bank or credit card company has on file. The transaction may be “pending” and not actually deducted from your account. How long a pending charge remains on your account is determined by your bank, and we're unable to reverse pending transactions.
Make sure the billing address you provided to us at myhopcard.com or on the Hop app matches what your bank or credit card company has on file. You may want to contact your bank or credit card company to make sure your billing address for your account is correct. Then try loading money on your card.