The most common cause of this is when the name or billing info you have entered does not exactly match the information attached to your card in your Bank's records. Double check this information first.
All other declined card issues on our web store at Hydrow.com will always require that you contact the card issuer (Bank, credit-card company, etc.) to sort out why your transaction was declined.
Card transactions on our website are securely through our vending partner Shopify and Hydrow Customer Care does not have access to your credit card transaction info or the ability to resolve card-decline issues.