[CA] Chart Orientation

I have a eS170 slaved to a C97.

I just finished the install of Auto Pilot EV400 with a S-100 Remote.

Upon commissioning, I noticed my chart orientation changed from "Course Up" to "North Up."

I changed it back to "course up" but it returned to "north up."

Why will it only accept North Up?

I checked FAQs and the instruction manual. It does not seem to describe this situation.