This error may appear when uploading your inventory .csv file if you have SKU's on the file that are not already in your ecomdash inventory and you did not check the box telling us to "Create new product if SKU does not match". If you want to keep us from importing these products that are not already in your inventory, leave things as they are and ignore the error. (Note: this is very useful if you are importing inventory files from a supplier for whom you do not sell all their products, only select products.)
If you do want ecomdash to import the new SKU's and create them as products in your inventory, navigate to Inventory > Inventory Management > Upload Inventory.
Then within the Upload Inventory details, you will want to select your .csv file and your import format. Then you will want to choose what actions you want ecomdash to take for your SKUs. For step 4, you if you want ecomdash to create new SKUs, you will want to make sure that box is checked.