I think this is because you have two different sites in your account, @ailik12. The site which is your Square Online Store and is connected to Square for payments is not currently published. Your other site, which is published and gives that error, is a regular Weebly site and is not currently connected to your Square account. You've got a couple options you can take. One is to connect the Weebly site to Square, which you'll also need to upgrade to a paid plan in order to sell with. The other option is to use the un-published Square Online Store site, add your items there, then publish and use that site instead. You won't need to upgrade the Square Online Store site in order to sell, so that seems like a better option.
