Shiprocket allows you to integrate multiple channels such as WooCommerce, Shopify , Magento , Amazon etc
For all the channels integrated , Inventory Sync Automatically runs in every 10 minutes. In case for any product inventory goes to Zero (0) , inventory sync is triggered instantaneously.
If you want to run inventory sync manually , you can Goto -> Products -> Inventory
Click “Sync Inventory” Button 
Just make sure that for your integrated channel , the Inventory Sync is On 
Note : In case your Channel Connector is broken, the Inventory sync will not work.