Are you still down?

I would turn off the power switch on the right upper side of the carrier cabinet.

Next I would reseat all the modules and make very sure they are fully seated in the cabinet and snapped in at the top.

After a few minutes I would turn the power switch back on and hopefully the phone sets will be working.

I've seen this happen when the AC power takes several hits on/off on/off...sometimes the processor light will still be green, sometimes red. Usually a power off for a few minutes then power on will resolve it.

Otherwise I would power off and pull all modules except the center processor and see if stations connected to it will work. If so, start adding the modules back one at a time.
DT98