Sire is black/tan dam is red/tan according to pedigree.fading pigment on a black and tan. Sable pups tend to darken with age . look at the pup picture , that is where he is at his darkest and then starts to lighten .
do you know who sire and dam were --- and they were ?
if sire and dam are black and tan then this pup can NOT be sable.
chances are that one of the grandparents said to be sable was in fact a faded black and tan. It doesn't matter , because sire or dam , an immediate ancestor has to be sable as sable does not perform as a recessive gene.