Hi,
Can you clear the cache to test and collect the problem report from the workstation if it doesnt work?
Exit Jabber
C:\Users\<User>\AppData\Roaming\Cisco\Unified Communications\
C:\Users\<User>\AppData\Local\Cisco\Unified Communications\
and delete everything under Jabber directory.
Also, on that workstation can you check if there is any other IM client installed like Skype or Lync? If yes then kindly uninstall it, clear the cache and check if it works/.
Aseem