With MailChimp already connected, the detail's **Status** tab includes a **Test connection** button that checks, on the spot, that the saved key is still valid against MailChimp's real API. **Requirements:** Admin role. 1. Open MailChimp's **Detail** and go to the **Status** tab. 2. Click **Test connection**. **Result:** "Connection successful" if the key is still valid, or "Couldn't connect: [reason]" if the key was revoked or changed (section 8). Remember that "Connection successful" checks the Marketing key, not the Mandrill one — if transactional emails fail, check the Mandrill key from section 3 separately. The example below uses Google Sheets again — with MailChimp connected, the same "Status" tab shows the "Test connection" and "Disconnect" buttons.