"However, still no ringing on either line. The ringer in the phone does work." How did you test it?

A 2565 needs no set amount of pairs to work. You need to read the BSP, and try to understand that these systems use wired features, rather than software features. You use as many wires as you need to, to get the job done. The ringer is factory-wired to the slate/yellow pair. It needs to be punched down (at least) on the T&R of a line to make it ring.

The screw holds the interrupter into the KSU.

Arthur P. Bloom
"30 years of faithful service...15 years on hold"