Instant Pot Sloppy Joes

Name: Instant Pot Sloppy Joes
Ingredients: 1 Tbs. canola oil; 1 small yellow onion, diced; 1 celery stalk, diced; 1/2 red bell pepper, diced; 3 garlic cloves, minced; 1 1/2 lb. (750 g) ground beef; 1 cup (8 fl. oz./250 ml) tomato sauce; 1/2 cup (4 fl. oz./125 ml) ketchup-style chili sauce; 1 Tbs. Worcestershire sauce; 1 Tbs. Dijon mustard; 1 Tbs. cider vinegar; 1 Tbs. firmly packed light brown sugar; 1 tsp. chili powder; Kosher salt and freshly ground pepper; 1 Tbs. cornstarch; 1 Tbs. warm water; 6 hamburger buns, split and lightly toasted