Issue symptoms
When I remove a domain that I used to host map the help center for a brand, then I try to use it in the help center of a different brand, I get the error host_mapping is invalid.
Resolution steps
Zendesk may have saved this host-mapped domain as cache for faster access. Wait an hour until the cache expires to update the domain for the next brand.
For more information, see this article: Host mapping - Changing the URL of your help center.