This invoice has already been paid.

-- Error-message(debug-mod must be tuned on) -- : This invoice has already been paid. For more information, please contact the merchant.
Your purchase couldn't be completed
There's a problem with the merchant's PayPal account. Please try again later.

Hi Team,

In our website we are using paypal as hikashop payment method.

Since 1day onwards while going to payment page it is getting following error

This invoice has already been paid. For more information, please contact the merchant.
Your purchase couldn't be completed
There's a problem with the merchant's PayPal account. Please try again later.

Please tell me how to retify this problem

Thanks
Karunakar