We have recently gone live with Manychat and our shopify ecommerce store.  We are running adset campaigns through facebook and use triplewhale (and facebook ads manager) for conversion tracking.  The TLDR to this post is this: We have seen a large ROAS drop in our facebook adsets, however overall store ROAS is up.  We believe there is a break in conversion attribution with Messenger.

One concern that we have is that when a user clicks on a facebook ads, then engages with the Messenger app to get the discount and Clicks on the link to Shop inside the messenger, that when they do checkout from there our systems are not able to see the passthrough of attribution from that type of shopping.Steps:
1: user clicks on an add from facebook app (mobile device) and opens up an in-app browsing session to bitsy bug. (allowing our system to track that the user came through)
2: they are on our website and then click on the discount code from Many Chats.  This then opens up the Messenger app.
3: Once they get the discount code inside Messenger, they THEN click on the Shop now button inside the messenger app and it opens up a NEW browser window in messenger to view the store.
4: If the user then checks out in the browsing window inside facebook messenger, does that sever the conversions tracking from the other browsing window inside the regular facebook app.

If this is true, then this setup kills our ability to properly manage and scale facebook ads as we rely on the accurate conversion tracking by adsets.  Does anyone have insights on this or how to fix it?