2X with Deepnet

I thought it's going to be very straightforward to use deepnet authentication in 2X. However, when I tried to do logon from 2X client, I was stuck by a strange error.

Code[01/0000000C] Account for user \\deepnetsecurity\username not found.

I was confused as this user truely existed in Deepnet application. It could be confirmed by looking through deepnet web-based management console. Also the function "Verify Deepnet user account names" provided by 2X didn't complain anything.

At the end, I turned to seek the help from Deepnet Support, they told me, in this case, the option "Use Principal Name" in application settings must be checked.

You can check the PDF version which has a few figures to help you better understand what I said.