Heat oil in Instant Pot on sauté mode. Add onion, cook and stir until softened.
Turn the Instant Pot off and add the tomato paste, garlic, Italian seasoning, salt and pepper. Stir and cook for 1 minute on the residual heat.
Add chicken broth to the still hot pan, and scrape the bottom with a spoon to remove any left behind bits.
Add potatoes, carrots, celery, tomatoes, green beans, corn, bay leaf and stir.
Put the lid on, turn the valve to sealing, and select Manual or Pressure Cook for 2 minutes. It will take about 15 minutes to come to pressure and begin counting down.
Once the cook time is over, let pressure release naturally for 8-10 minutes before opening the valve and removing the lid (this is to prevent the splatter that can come when pressure cooking soup).
Stir in the spinach, adjust seasonings to taste (add 1 teaspoon sugar to balance tomato paste if needed) and serve.