When you pay for something with your PayPal account, you can follow the processing of your payment through the "Status" column in your account overview. First, the system places a temporary hold on the purchase amount in your account, making it unavailable to you. The merchant then has three days to capture the payment. If the merchant doesn't collect the funds within three days, PayPal marks the transaction "expired" and returns the funds to your available balance.
Equipment Failure
A merchant may fail to complete a transaction because of payment processing errors. For example, an equipment timeout may prevent the merchant from receiving an authorization from PayPal. In that case, PayPal has placed a temporary hold on the funds in your account, but the merchant believes that the system has denied authorization and doesn't follow up to collect the funds. Without a specified expiration period, your money could stay on hold until you dispute the transaction.
Other Expiration Reasons
Authorizations may also expire for other reasons, such as a change in your order or a delay in processing your order. PayPal allows merchants to capture payments for up to 29 days after the original authorization, but the company only guarantees the full payment during the initial three-day period. If you don't understand why a payment has expired or how the merchant intends to complete your order, PayPal recommends that you contact the merchant to learn more.