Current User: '%1' Client Access server "%2" tried to proxy Web management traffic to Client Access server "%3". This failed ...

Current User: '%1'
Client Access server "%2" tried to proxy Web management traffic to Client Access server "%3". This failed because "%3" couldn't verify that the Active Directory account "%2" used to authenticate has the necessary access rights to send Web management proxy traffic. Verify in the IIS Manager that Windows Authentication is enabled in the internal 'ECP' virtual directory and that 'Get-EcpVirtualDirectory' reports 'WindowsAuthentication' as 'True' in the internal server '%3'.