If the sync runs but specific customers are absent in Brevo, it is usually a data-quality or consent rule, not a broken connection.
Step 1: Confirm the Sync Itself Is Healthy
If no contacts are syncing at all, this is a connection problem instead. Start with data not syncing. Continue here only when some contacts arrive and others do not.
Step 2: Check the Common Reasons
| Reason | Explanation | Resolution |
|---|---|---|
| No email address | Brevo contacts require a valid email | Expected. Guest checkouts without email cannot sync |
| Marketing consent off | Customer did not accept marketing | Working as intended; respect consent |
| Invalid email format | Typo or role address rejected | Clean the source data in Shopify |
| Still in backfill | Large historical import in progress | Wait for the backfill to finish |
| Filtered by your segment | Contact exists but not in the list you are viewing | Search the full Contacts table, not the segment |
Step 3: Search the Full Contact List
Before assuming a contact is missing, search the entire Brevo Contacts table by email. It is often present but excluded from the segment you were viewing.
Step 4: Validate One Customer End to End
Pick one missing customer in Shopify. Confirm they have a valid email and accepted marketing. Trigger a manual sync in Tajo, then search Brevo again. This isolates whether it is a data rule or a sync gap.
Consent and Compliance
Tajo respects Shopify marketing consent. Contacts who did not opt in are intentionally not synced as marketing contacts. This protects your sender reputation and keeps you compliant.
Next: understanding data sync.