If a credit sale doesn't complete, it'll remain open for up to 60 days from its creation date. Unfilled orders will expire after 60 days and any unsold credits will be returned.
In some cases, Listia may also expire your sell order prior to the 60 day period if the rate you've chosen is too low and unlikely to sell. If this happens, all unsold credits are returned to your balance.
In order for your credits to sell faster or within a reasonable time, consider canceling your order and creating a new one and setting a different price.