can not add an administrator in SEP manager

in the past , I use the follwing method to add an administrator in SEP manager without any problem,

Admin->add an administrator->Directory Authencation-> when test account ,the result is 'Directory account authenticated'.

in recent when i add a new administrator ,the error message pops up:

but I can use the this domain account to login any pc in the domain successfully, which can verify the 'password' of this account is correct. And I login DC and reset the password of this account and try again, without luck.

As I remmeber the only change I did during the period is ugprade SEP Manager fron version 12.1.1 to 12.1.3 . I am not sure if the uggrade is related to this problem,

please help me out

thanks

Best Regards

Michael