Hi Rick, Check your site now.
There were some default settings changes while updating the site from Sellacious 1.4.x to Sellacious 1.5.3.
Please note these settings for the future whenever you're updating your site.
1. Settings-> Global Configuration-> General tab-> Marketplace-> Enabled
(When you want to set your shop for multiple sellers then enable the marketplace.
When you don't want to set the shop for multiple sellers then disable the marketplace.)
2. Settings-> Global Configuration-> Seller tab-> Default Seller
Set the default seller who you want to sell the products by default.