If it is an old email address that used to be linked to your Paypal account then you can call them up and they may be able to sort it If it was just a typo and you cannot create that email address ad add it to Paypal then all you can do is ask the buyers to cancel the payments and tel them you will send them a Paypal invoice. Some inexperienced members may be unwilling to do ths as they may think it does not give them buyer protection.