When the NTLM proxy authentication is adopted, a user uses the network extension client to connect to the virtual gateway. If the proxy user name of the network extension client exceeds 20 characters, the user login fails.
Contact the administrator of the proxy server to change the user name of the proxy server to less than 20 characters.
The NTLM authentication is realized through the AD. The Windows domain controller can only authenticate the first 20 characters. Thus, if the user name of the proxy server exceeds 20 characters, the login fails.