NO, it is never too late to potty train a dog. Here's How to Start. [learn more details at How to Potty Train a Service Dog]
1: Commit yourself to a house training schedule
Devise a schedule and stick with it. The schedule should include mealtimes, play sessions, training sessions, going outside and taking naps.
2: Supervise your dog
To keep an eye on your puppy the whole time, you should limit the access area in the house. If you put him behind some baby barriers or in a playpen, this would effectively control his area of activity. This should help you to notice the subtle signals of your puppy when he is ready to go outside.
3: Advanced training
After completing step 1 and step 2, it is time to train it with potty commands.