I came across Sellbrite some time while looking for a Shopify integration tool with online marketplaces, but I finally decided to go with litcommerce. They do serve necessary features for a Shopify integration process, from bulk product listing to real-time sync to order management. I'm using the extension to integrate Shopify with Etsy and Google Shopping and quite satisfied with it. It's not like I bring Sellbrite down or anything, but if you are struggling with Sellbrite you can take a look at litcommerce instead.
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