Turn on the Instant Pot's 'Sauté' function. Add olive oil, then carrots, celery, and onion. Sauté for about 3-5 minutes until they start to soften.
Stir in the minced garlic and cook for 1 minute until fragrant.
Add the cabbage, green beans, diced tomatoes, vegetable broth, Italian seasoning, salt, and pepper. Stir well. Cancel the 'Sauté' mode, close the lid, and set the vent to sealing. Set the Instant Pot to manual high pressure for 12 minutes. It will take time to come to pressure.
Once the cooking time is up, let the pressure release naturally for 10 minutes before quickly venting the remaining pressure.
Stir the soup, taste, adjust seasonings if needed, and serve warm. Garnish with parsley.