We are struggling for quite some time now with these 2 errors. I asked around and these are the x2 solutions that I found out:
1. New Domains Sending Data Solution -> Facebook Support told us in order to fix this issue to create an "allow list" on the events manager and add our domain there, this way they say it will be solved. I did this yesterday and marked the error as "resolved", but at the moment is still showing at previously detected but still detected today.. finger crossed it will disappear..
2. Regarding the deduplication, this is a big issue that appeared on our account 4 days ago and since then even with 500-700 budget per day, there are no sales!! We went from 5-6k in sales per day to 200-500 USD... and we are desperate & scared, to be honest.
I found a potential solution: That you should switch from Maximum sharing to Conservative sharing on FB App at Shopify BUT also to make sure you let only "External_ID" ON at advanced matching settings on the business manager, wait for 24-48 hrs and then go to Maximum again. I did this today and again finger crossed it will work..
Do you have any other solutions for this type of issue? Do you still see a big difference in conversions lately..?