If you go to another phone, and dial 100, does it ring the operator station? If it does, the port is not bad.

Is station 100 the first port on the block? I remember an earlier version of software that you had to put the actual port number instead of a swapped port. So if ext 100 was punched to port 6 (105), you had to enter 105 os the operator station even though the phone had 100 on the display. If the phone in the port defined as an operator was not working, I thought you would get a reorder tone when zero was pressed.

Tip and ring, the work of the devil!