Hi Ralph!
Try to go to form Emergency Services -> Default CESID. Does "Enable automatic CESID Updating" is enabled?
In that case, MCD is warning you that it's not possible to get automatic CESID assignment for a phone (phone is connected to an unknown switch). You will be able to identify that phone in CESID logs.
If CESID management is manual (by entering manually CESID numbers to all phones) on that PBX, just try to disable automatic CESID updating and alarm should clear.
Hope that helps!