It appears Voice mail is not ringing your ext.(205)
could it be that the port it needs to access your system. is not connected. you might want to check those cables / slt ports that go to the voice mail for dial tone.
Once you reach that main message you are in voice mail. When you dial an ext. it needs to access your system and send those those digits. back to the system to ring your phone. once it recives busy or ring no ans. then the call goes to your mail box. Make since?