Stock not syncing to Shopify. 0 stock is already updated on the Shopify from Our System
Could you tell me a little bit more about your system? It is possible that if we do not have an already established integration with your system, you might need to look at setting something up for it to work.
If your system is your own, you might need a custom app to make this work - have you already considered contacting a Shopify Expert? If not, I would recommend you look into this - they are freelancers trusted in the Shopify Community and they charge their rates based on the work that they do. You could describe what you need and work with them to establish an integration for the stock to sync.
For fast, bulk inventory setting you could replace your system with Mixtable's Google Sheets-like spreadsheet interface to manage your Shopify product inventory. Mixtable works like Excel/Google Sheets, so you can add any number of worksheets/columns to hold data, and syncs data to and from Shopify automatically.