
Take her to the vets to see how many pups and if they are still alive.
Only one pup can lead to one cause of primary inertia[labour never starts] because the one pup isn't enough to trigger the hormones which start the labour off.
Over how many days was she mated? Is 64 days from the first mating? Sperm can live as long as 7 days waiting for the eggs to ripen so we never know exactly when the eggs become fertilised.
Good Luck, keep us posted.