Hello all, Came from an Avaya background and new to this system. Norstar Plus Compact ICS. System had 4 line keys on all the phones(6 in total). Now line 3 seems to be missing when pressed from a phone. I verified that the POTS line is working and even swapped it with line 4 so it's not a telco issue. How can I verify that the port for line 3 didn't go bad? Is it possible the system lost programming for line 3 but not 1,2 or 4? Can I program it as a line 5 and punch down onto another port and how would I do so? Correct me if I'm wrong but someone told me this is only a 4 line system.