Below are the most common reason and solution for this problem:
1.) Update Woocommerce & Knawat Dropshipping plugin to the latest version.
2.) API keys are inserted and Valid.
3.) Products are added to store at app.knawat.com if already added, then do the sync.
4.) WP_CRON needs to be enabled.
==> Our plugin uses WP Cron for synchronizing products and Orders into the background, so please confirm its not disabled on your website
5.) Port 80 and 443 should be open.
==> Port 80 and 443 are needed Open for Knawat Dropshipping plugin get working. these ports are open on all hosting but because of some reason, its get closed on some shared hosting. so, please check if port 80 OR 443 close on your web host then please contact your hosting provider for open it for you.