Are the products approved by the Admin prior to when they go live?
Yo!Kart provides a setting to enable/disable admin-approval on products added by sellers. If this setting is enabled, all the products added by sellers will be marked as Unapproved until the admin marks them as Approved. Only the Approved products will be displayed at the front-end. However, if such a setting is disabled, the products added by the sellers will be displayed at the front-end.