Did you originally sign up on Scott's Marketplace as a shopper and then, when you clicked on "Start Selling" and entered your email address you were told that the "account already exists?"
No need to create a new account with a new email, simply shoot us an email asking us to switch your account from a buyer's account to a seller's account and we'll make it happen! Contact us here.
We are currently working a solution that will resolve this issue completely in the future. Thanks for your patience in the meantime!