I have a C/Con 8 daisy chained to a C/Con 16. The 16 shows AC, but the 8 is only displaying P0. I am unable to find any information about a P0 message.
P0 indicates no communication between the host adapter and that particular C/CON.
I recommend checking the cable connections and termination on the C/CON concentrator.
If this does not pan out, I recommend contacting Digi Technical Support.