Same Event ID Received for Many Event Instances

I configured everything like in this how to: https://gtm-server.com/facebook-conversion-api-for-shopify/

Now I get also the following error for View Content and Add to Cart events

You’re sending the same event ID for many instances of your AddToCart events. Event IDs are unique identifiers that are used to deduplicate identical events received from your pixel and the Conversions API so they’re not counted twice.

Please help to fix

Did you install the Facebook app for Shopify and enabled maximum tracking? The solution from this post https://gtm-server.com/facebook-conversion-api-for-shopify/ takes event ID from the Facebook app for Shopify.

Try to test FB CAPI inside the FB testing tool and Google Tag Manager preview mode. It will help to check if event ID is added to the data layer and server container.