Charge Wizzard Not Charging

[Bill.vannuys]

I have a 2014 3735MK with a Progressive Dynamics PD 4590K18L converter.

In the last week my charge wizzard is not charging the batteries.i have a voltmeter built into my battery box that gives me a constant voltage condition of the batteries. Normal reading on shore power is 13.2 or 13.6; however, my reading finally dropped to 12.0 volts (just above 50%). I verified accuracy with a voltmeter. I placed an external charger on the batteries and voltage went back toward a full charge after about 12 hours.
Charge wizzard is flashing once/second and sometimes constant (I think that is the normal and boost modes).

Only thing I can figure is fuses or defective converter.

Anything special I must do to check the fuses (unplug shore power and battery switch off?).

Would that be the four 25 Amp fuses above the charge wizzard indicator light?

Any other ideas?

Battery cables have not been recently disconnected (so no accidental reversal).

Thanks for any response!