14 answers
That error usually points to a missing or outdated Remote Site Setting entry. The Mailchimp package makes a callout during the auth step, so you’ll want to check that the exact endpoint shown in the error is added as an active Remote Site and that your org’s My Domain isn’t blocking the redirect.
If the native package keeps failing, some teams end up switching to an external connector instead. For example, Skyvia (https://skyvia.com/data-integration/integrate-salesforce-mailchimp) can sync Mailchimp audiences and Salesforce contacts without relying on the managed package or Remote Site Settings, but I’d try fixing the callout entry first, that’s normally the root cause here.
