Shopify + Klaviyo: When a flow looks healthy but repeat purchase underperforms, what do you check first?

When a flow looks healthy but repeat purchase is underperforming, what do you check first?

I’m trying to understand a specific Shopify + Klaviyo failure mode.

Sometimes the dashboard looks normal, but underneath:

- the expected customer never entered the flow
- eligibility or suppression excluded someone unexpectedly
- an event arrived late
- attributed revenue made the flow look healthier than it really was

For people who have debugged this in real stores:

What was the earliest signal that told you the problem was underneath the reporting rather than the messaging itself?

I’m especially interested in real examples where the dashboard initially looked fine.