How this differs from Mailchimp resource-not-found errors
This is a distinct failure from the data-center list-ID mismatch covered separately — here the credential and list ID can both be correct, but the actual webhook-registration call Mailchimp performs on activation still fails or silently does nothing. Community reports of "trigger not activating" specifically describe registering an API key and pointing it at real subscriber data, then hitting a wall only at the point of turning the workflow on.
Check webhook-registration-specific causes
- API key permission scope: confirm the key was generated with full account access rather than a restricted or read-only integration-specific key, since webhook registration is a write operation on the account's webhook settings, not just the audience data.
- Existing webhook on the same n8n instance URL: Mailchimp associates webhooks per-audience; if a previous, now-orphaned Mailchimp Trigger workflow already registered a webhook at the same n8n URL and was deleted without deactivating cleanly, a new activation attempt can conflict rather than cleanly registering.
- Account-level webhook support: some Mailchimp plan tiers or account configurations restrict webhook management; confirm your account tier actually supports the webhooks API before assuming the n8n side is misconfigured.
Check what Mailchimp already has registered before troubleshooting further
Rather than guessing whether a stale webhook exists, call Mailchimp's own list-webhooks endpoint for the specific audience to see exactly what is currently registered, including the URL and event types — this immediately tells you whether an orphaned registration from a deleted workflow is sitting there conflicting with a new activation attempt.
curl -u "anystring:your-api-key" \
"https://<dc>.api.mailchimp.com/3.0/lists/<list_id>/webhooks"
# Replace <dc> with your data center (e.g. us21) and <list_id> with your audience ID.
# Look for any existing webhook entry pointing at your n8n domain.
Fix by clearing stale webhooks and re-testing activation
In Mailchimp's own Audience > Settings > Webhooks page (or via the API call above), check for any existing webhook pointing at your n8n domain from a previous or duplicate workflow, and delete it manually if it is orphaned — n8n cannot see or clean up a webhook it did not itself just register in the current session.
Deactivate and reactivate the n8n workflow after clearing any stale webhook, watching for a new entry appearing in Mailchimp's webhook list at the moment of activation, which confirms the registration call actually succeeded this time.
Sources checked for this guide
The community report below describes the activation-specific symptom distinct from ordinary data or credential errors; the webhook-check method comes from Mailchimp's own API reference.
Frequently asked questions
My API key works for other Mailchimp nodes — why does the Trigger still fail to activate?
Webhook registration is a separate write permission from reading audience or campaign data. Confirm the key has full account access, not a restricted scope that only covers read operations.
Could a deleted n8n workflow be the cause, even though it's gone now?
Yes. If that workflow registered a Mailchimp webhook and was deleted without properly deactivating first, the webhook can remain registered on Mailchimp's side and conflict with a new activation attempt at the same URL.
How do I check what webhooks Mailchimp already has registered?
Call Mailchimp's list-webhooks API endpoint directly for your audience ID, which returns every currently registered webhook and its URL — this is more reliable than trying to find the same information in the dashboard.
How do I check if my Mailchimp plan supports webhooks at all?
Check Audience > Settings > Webhooks directly in your Mailchimp account — if the page and its management options are not available or restricted, confirm with Mailchimp support whether your account tier supports webhook management.
