Mix balsamic vinegar, beef broth, soy sauce, brown sugar, and Worcestershire sauce in a small bowl. Pour into Instant Pot.
Add potatoes, beef chuck roast, and carrots.
Cook on Manual + High for 45 minutes.
To thicken sauce, remove beef, onions, carrots, and potatoes. In a small bowl, mix ½ cup of pot roast broth with cornstarch making sure there are no lumps. Add mixture back into the Instant Pot with the gravy. Cook on Sauté setting until the gravy has thickened. Pour over roast and potatoes.