I have added a 4th CO line to an old NEC Electra system, and just found out none of the phones (Line 4 button) will actually Select the COL 4.
Additionally, no station rings, and no Line 4 button lights are on with ringing COL 4.
I have tested the CO line at the modular plug going into the COI(4) unit, all good.

Reviewing the programming table of contents, I'm unsure which command MBs would control this.
Lines 1-3 operate properly.

Seems like it would be a COL access by station/port command, but there is no such command.

Any advice appreciated.
Please try to be specific with programming references.
Thanks