netbackup sql server client not working

Hi all,

I am going to use netbackup to backup the ms sql server 2008 db,

however, when i setup the sql server properties, no matter on the db server itself or the netbackup management server,

it also failed.

the error is "Application coneciton failed for %SERVERNAME% Please select a differetn SQL Server host and instance, or press 'canel' to exit the Netbackup for SQL Server Graphical User Interface.

do you guys know what's going on?

I pretty confirm the user id and password are working well.

Thanks