Lync 2010 client not sign in

Hello,

One of users cannot login to lync 2010 client.

when the user want  sign on to lync, get below error message ;

"cannot sign because lync server is temporarily" However, other users can login the system.

I insert lync server address as manuel conf. from the client. not change anything.

After than, I install wireshark and not find any traffic  to lync server from lync 2010 client. 

I can run telnet command as "telnet lyncpool.domain.com 5061 or 443"

and I can see telnet traffic from wireshark.

Whay can I do for resolve this problem ?

Thanks