Set the Instant Pot to sauté mode and heat olive oil.
Add onion, celery, and bell pepper. Cook until softened, about 5 minutes.
Stir in garlic and sliced sausage, cooking for another 2 minutes.
Add chicken broth, diced potatoes, Cajun seasoning, paprika, and black pepper.
Cancel sauté mode. Seal the Instant Pot lid and set to pressure cook on high for 10 minutes.
Once cooking is done, quick release the pressure carefully.
Stir in heavy cream and taste for salt. Let the soup rest for 5 minutes before serving.
Garnish with chopped green onions and enjoy.