If the application is hang and you crash the browser, in next login user gets error >”Maximum communication toolbar error”
In this case go to Tools->Communications->Reset Active Session Counts option, logout the user and Login again.
In some exceptional cases like Driver hang, Crash, Siebel session hangs and unsuccessful logout, the subsequent Siebel login will not display communications toolbar. To display the communications toolbar in the next session,
Click on Tools > Communications > Reset Active Session Count.
The agents have to logout from phone and re-login again to Siebel.