This support article covers how to map warehouses and vendors to products and SKUs. These are basic concepts, however, if not understood they can cause much confusion.
1. Warehouses are mapped to Vendors.
2. Vendors are mapped to Products (and SKUs inherit the product mappings).
See How to Add/Map New Warehouses to Products and SKUs through Vendors.
Each time a new warehouse or vendor is added they will need to be mapped or they may not be visible in all areas of Lead Commerce.
Please Note: Another mapping to be aware of is the Product Type. Each time new vendors or categories are added they will need to be added to any Products Types that will be using them.