Did you do the approach in CWS? The only aircraft I flew with CWS (747-300 with CWS in manual mode) would require all three autopilots to be switched from Command to Manual which clearly wasn't going to happen at such short notice.
Cat IIIb in a 744 with a DH of 0' FLARE GREEN comes in at 52' RA which is below MAB. You have to let it land. Ouch!