Northwestern thinks I can walk even though my left leg is paralyzed

My Northwestern Disability policy has a presumptive total clause which pays lifetime benefits for loss of use of one hand and one foot. They Have claimed I do not fulfill their definition because I can walk. My left foot is paralyzed. My sensation is abnormal, I cannot balance and cannot walk without a cane and functional neuromuscular stimulator or AFO. I receive benefits nowfor disabilityand this clause would only be important after I am 65.