Ok...I synced my Shopify and Quickbooks Online with the 'connector' because it said you can sync products and inventory levels. I'm having trouble

I am trying to sync inventory and products between Quickboos Online and Shopify. 

Inventory deducted via a quickbooks invoice will also be deducted from Shopify inventory of the same product.

Shopify inventory deduction via online sale will also be deducted from Quickbooks inventory of the same product.

Is there a way to do this? Do I need a 3rd party app?

If so, what is the best app to use?