Inventory sync between shopify and ebay is set in the following ways    

By importing ebay items to shopify store    

By listing shopify products on ebay    

Mapping ebay items with shopify products    

To set inventory sync settings, please navigate to Sidebar Menu and click on “Settings”. Then settings page will be open as shown below    

In Settings page, click on “Inventory Sync” tab. Then inventory settings section will be open. 

In the upper section “Shopify → eBay inventory sync preferences”, these are the settings related to shopify inventory changes which effect on ebay inventory. 

• Enable Shopify Inventory Sync: Click “Yes” to enable shopify inventory sync with ebay 
• On product delete/inactive: select the option dropdown which effect on ebay when shopify product deleted or inactive 
• Notify me On Product Disable/Inactive: A notification is sent when a shopify product is disabled or inactive   
• On Product Price Change: select the option from dropdown “change on ebay store” or “do nothing”  which effect on ebay when shopify product price is changed   
• Notify me On Product Price Change: A notification is sent when a shopify product price is changed   
• On Product Quantity Change: select the option from dropdown “change on ebay store” or “do nothing”  which effect on ebay when shopify product quantity is changed   
• Notify me On Product Quantity Change: A notification is sent when a shopify product quantity is changed   

In the lower section “eBay → Shopify inventory sync preferences”, these are the settings related to ebay inventory changes which effect on shopify inventory. 

• Enable Ebay Inventory Sync: Click “Yes” to enable ebay inventory sync with shopify 
• On product delete/inactive: select the option dropdown which effect on shopify when ebay product deleted or inactive 
• Notify me On Product Disable/Inactive: A notification is sent when a ebay product is disabled or inactive   
• On Product Price Change: select the option from dropdown “change on shopify store” or “do nothing”  which effect on shopify when ebay product price is changed   
• Notify me On Product Price Change: A notification is sent when a ebay product price is changed   
• On Product Quantity Change: select the option from dropdown “change on shopify store” or “do nothing”  which effect on shopify when ebay product quantity is changed   
• Notify me On Product Quantity Change: A notification is sent when a ebay product quantity is changed