i have found in the past that an older w,hood cock , never having even seen his hen for weeks will [on occasions take to a pair of 2 day old yb,s the day b4 basketing,]without seeing the hen ,,, off course the babies will need renewed[handy to have another pair on babies so you can keep changing them quite often as the cock would have no milk,,,i was 15th gold cup nat, with a cock this way
a young hen sitting on about 5 eggs 3 days b4 basketing ittl spend three days trying to tuck the eggs under it this will make it keen
a hen or cock sitting on its first eggs of the season [later in the season ]after sitting overdue and beginning to lose interest put a pair of ybs under it[ often good with a barren hen ],and keep the cockand hen separated ,not seeing each other,both think their looking after the yb,s themselves
an old cock , driving some times works with certain cocks
no matter what you try , if the bird is not at its fittest ,nothing will work