Most likely, you have been trying to make a payment with an unverified PayPal account. Account verification is a service PayPal offers, to increase your PayPal account security.
Please understand that we do not accept payments made from unverified PayPal accounts for security reasons.
If you want to use your PayPal account to make a payment, then please follow the instructions made available by PayPal to verify it. Once that process has been completed, you will be able to make payments using your PayPal account.