We are trying to access our Zendesk account via https://www.zendesk.co.uk/login/#login and require our subdomain to do this. We cannot recall what this is. The reminder asks for an email address to send it to, but again we do not know this either and all those we try receive emails saying that it's not registered.
A chat function or a pone number would be helpful, but you do not provide this.
It seems you have a legacy Zendesk Chat account which uses a different URL for login.
Kindly login via http://dashboard.zopim.com/ in order to access your Zendesk Chat account.
Hope that helps!