Heat oil in the cooker. Add sausage and cook until no longer pink, about 3 minutes. Stir in onion and garlic; cook until softened and translucent, about 3 minutes. Stir in Italian seasoning, salt, pepper, and red pepper flakes. Add potatoes and chicken broth. Close and lock the lid. Select high pressure and set timer for 5 minutes. Allow 10 to 15 minutes for pressure to build.