ROAS recovering to 2.9 - Check you Purchase events are firing every time. Post-purchase Shopify app broke 80% of Purchase events for me.

Like most of you my ROAS tanked from March. I put it down to Andromeda. I did lots of things I read in this subreddit to react accordingly.

But I noticed too daily performance was not stable, and had not been for months.

If Andromeda was the cause I would expect consistently bad results. Not good one day, 50% down the next, 35% up the next, then back down 25% ad infinitum.

So I delved deeper in my tracking code and manually tested. I noticed some days Shopify and Facebook showed vastly different conversion numbers. Some days off by 10% (expected) some days off by 50%

Some days Facebook did not know about half the sales it caused.

So I did 5 real purchases from my website manually and saw 4 out of 5 times the post-purchase upsell page was broken (it shows "also buy this for 20% off!")

Oddly this being broken prevented my Facebook Purchase event from firing 4 out of 5 times.

So Facebook was getting page view, add to basket, checkout started, but for 80% of customers no Purchase event.

This obviously prevents Facebook from optimizing targeting for purchase, and would unlearn what a "good" customer looked like. Dropping these tracking events made it impossible for Facebook to optimize. Bad tracking days would undo what Facebook learned from good tracking days.

Once I turned off the Shopify App that shows the post-purchase upsell, ROAS started climbing. It's at 2.9 right now.

So lesson learned:

• Compare Facebook and Shopify conversion metrics daily. React accordingly if they disagree

Note I don't use CAPI as when I turned it on ROAS dropped further, so I got scared and turned it off. I will probably turn it back on in future.