I have a client with a shop that has been operating for around 6 months with over a thousand orders.
None of the orders have any order conversion tracking information (https://help.shopify.com/en/manual/orders/conversion-summary)
I am trying to discern what controls how this information is passed from a user session to the order so I can figure out how to ensure this information is collected.
Notably - this is an entirely custom theme that leverages the Storefront API to add products to the checkout.
There are also some apps installed. Happy to go into more detail on these if necessary.
How about other analytics? Like product views, sessions, etc. All these events are recorded by Shopify's internal tracking library trekkie, do you see any of these firing in the browser console when navigating through the store?
It might well be the Shopify event tracking library is not present or misconfigured considering it's an entirely custom theme.