Hi! Just adding an update for anyone landing on this thread 
There’s now a more complete guide covering the most common reasons why orders may fail to sync with Shopify.
You can check the updated article here:
https://community.funnelish.com/t/why-orders-are-not-syncing-to-shopify-and-how-to-fix-it/9872
Hope this helps! If you’re still experiencing issues after going through the guide, feel free to reach out to support or share more details here so we can help.