How do you fix depression of a dog?

Dogs are pack animals and social creatures. They respond to love and attention. Include the dog in some of your activities and reward the dog with a treat now and then. Take it for walks or a swim or even a drive. Make a place for the dog in your bedroom, a blanket on the floor will do, it makes them feel like part of the pack, you are the Alpha, it is up to you to give the dog reason to feel wanted and loved. Your dog might need to be played with more. Give your dog more attention. Play with your dog outside. Take you dog for a walk. You may need another dog around to keep your dog entertained when you are at work.