If your dog can't bark it may be the result of several factors. Some dog breeds don't bark in the typical sense. Some medical conditions can cause a lack of barking. Some owners intentionally de-bark their dogs.
If your dog has undergone surgery, she may not bark for a while, or her bark and voice may sound different. This is the result of the tube placed in the dog’s windpipe during surgery. This generally resolves itself in a few days.
Hoarseness and Laryngeal Paralysis
Sometimes a dog will stop barking because he is hoarse from constantly barking. Dogs can suffer from a condition called laryngeal paralysis, which occurs when the larynx doesn't open correctly. Labradors are commonly afflicted with this condition.
A tumor on or near the larynx can cause a dog to stop barking.
Some dogs do not bark like other dogs. These dogs make noise, but they don't bark in the typical sense. The Basenji is a bark-less dog. Although the Basenji doesn't bark, it will make noises that sound like yodels, howls, crowing and screeches. Some of these dogs appear to humor sing, notes Terrificpets.com. Beagles don't tend to bark, although they can. Instead, they bay, which is a long, deep, drawn out sound common among hounds. Hunting dogs may bay to alert the hunters and other dogs to their location. The New Guinea Singing Dog doesn't bark. This wild dog originated in New Guinea. The sounds that this dog makes include single, trilled high notes. They can growl and rumble musically but they don't bark. The Alaskan Malamute and the Siberian Husky don't bark. Instead, they talk. They may a wooo sound when are communicating with their owners or with other dogs, or when they are happy and feeling emotional. Huskies are quiet dogs that do not normally bark, but they are strong howlers. Howling is a sign of a pack-oriented animal. If a Husky or Malamute lives among barking dogs, she may assume a type of bark, but it's not a true bark.
If you have inherited your dog, is it possible that the previous owners had the dog debarked? This is achieved by a surgery called vocal cordectomy. The folds of the tissue that make sounds, and which are around the vocal cords, are removed and the dog can no longer bark.