A user may find that they are unable to update a CNAME from within the Dashboard. The following error will appear in a pop-up:
There was a problem updating your CNAME, please contact support
The UI for setting the domain name has a very strict validation, so it may just be rejecting this domain.
The best way to set the domain is to use the Tyk Dashboard API, to obtain the organisation object via a GET request and then update the object using a PUT request with the relevant CNAME added to the body of the request. Restarting the process will then set the domain.