Set the Instant Pot to sauté mode. Heat the olive oil, then add the onions. Cook for 3-5 minutes, stirring occasionally, until translucent. Add the celery and carrots and cook for an additional 5 minutes.
Add the garlic and cook for an additional minute. Add the tomatoes, green beans, kale, and Italian seasoning, followed by the broth.
Lock the lid on the Instant Pot and set it to cook on high pressure for 2 minutes. (Note: It takes about 15 minutes for the soup to come up to high pressure).
Once the soup has finished cooking, let the pressure release naturally for 10 minutes before opening the valve and removing the lid (this will help to prevent splatter).
Stir in the lemon juice, beans, salt and pepper. Taste and adjust seasoning, if desired.
Ladle into soup bowls and top with fresh parsley, if using.