Your clients are trying to pay you and they encounter the error message: ”We can’t process your payment right now, so please try again later” after entering all their credit card details in the PayPal interface. They also might be getting looped back to the beginning of the payment process over and over again.
The value of the transaction has pushed your client’s credit card over the “Guest Checkout” transaction limit -OR- your client’s credit card/email address is associated with an existing PayPal account.
Your client must sign up for PayPal and log in to pay the invoice – they can still use a credit card once they are logged in.
As the FreshBooks account owner, you can sign up for an upgraded PayPal account like Website Payments Pro, so that your clients stay within the FreshBooks interface when trying to pay your invoice and don’t hit security roadblocks.