Attribution Discrepancies on Shopify Clients

[IntAdm]

I Need to know why the orders placed by using my tracking link are shown as Direct / Organic source in Shopify Reports. I am having this issue with multiple Partners all using Shopify for their online stores.
Are there any required parameters in the URL which I am missing ? I am using UTM parameters for passing the required information to the final pixel being fired. I believe the same is being used by Shopify for populating data into the reports. 
Please help with possible fixes to reduce the discrepancy. Currently, I am losing 40%-50% of my orders due to them being tracked at my end but Shopify attributing them to Organic/Direct Source.

[books_R_us]

Following because we're seeing the same issue as well. Losing 66% of our attribution data on both referral_site and landing_site across both a standard and headless integration, which is super weird.