If you deleted all products from your store and want import them again you need to delete the instance and create it again.
From your account on knawat go to web stores.
Click Actions then choose Settings.
- Scroll the page to down and click Delete this store and all products
Now all Products will be deleted , to import them you need to reconnect your store and start importing products.
Note : Before starting re-import products from knawat make sure all products are deleted from your store .