API “Connected” but not working

[2024-11-09 10:59:04] ERROR: Form 288 > Mailchimp API error: 401 Unauthorized. API Key Invalid. Your API key may be invalid, or you’ve attempted to access the wrong datacenter.
Request:
GET https://us13.api.mailchimp.com/3.0/lists/b549513220/members/1b841bd3f67fa566b89de854a7139e32
Response:
401 Unauthorized
{“type”:”https://mailchimp.com/developer/marketing/docs/errors/”,”title”:”API Key Invalid”,”status”:401,”detail”:”Your API key may be invalid, or you’ve attempted to access the wrong datacenter.”,”instance”:”9648037f-65cc-bf15-6c1b-34e2bcb52292″}

The API key that was working before and a newly generated will neither work.