Thank you very much for your answer.
So I understand that the variables are not defined as it is before the data is inserted (check out initiation). However, the product id is not taken into account while adding an item to the cart.
I also modified and changed the “Store: None” to “Store Cookies” on the web container side. Is this what I should do?
I found a page on the stape site that uses GA4 for FB API setup, but since I am using the Data Tag Client, do I have to use GA4?
Link: How to Setup Facebook Conversion API + Events Deduplication & Hash User Data
To summarize my situation, the server container is set up, the link between the two containers is linked, I only have my variable problem left…
Thanks in advance for your help!