My agents see the below error when they try to sign in to my host-mapped account: yoursubdomain.zendesk.com refused to connect.
The error yoursubdomain.zendesk.com refused to connect comes from privacy settings blocking third-party cookies. Host-mapped Zendesk accounts have the sign-in page URL support.yoursubdomain.com and the underlying Zendesk page related to the sign-in cookie yoursubdomain.zendesk.com. Some web browsers, ad-blockers, and privacy-related extensions will block cookies because of this URL mismatch.
To solve this issue, ensure the browser allows third-party cookies from Zendesk.
You can find the instructions to allow third-party cookies in Chrome in this article from Google Chrome Help: Clear, enable, and manage cookies in Chrome.
If your browser has ad-blockers, turn them off to see if this allows you to sign in. Some ad blockers have their own list of exceptions. If that is your case, add yoursubdomain.zendesk.com to the allow list.
For more information, see the article: I am having trouble logging in to Zendesk.