Agent do not hear the phrase you are the only person in this

When agents log in they can not hear the phrase"you are the only person in this confrence".
I am using x lite soft phones with vicidial version 2.05
The agents can hear the message on some of my phones but not on others.
I am using x lite soft phones with vicidial version 2.05
The agents can hear the message on some of my phones but not on others.