Turn on saute mode. Add olive oil. Cook onion, carrots, celery, and garlic until soft.
Add chicken, chicken broth, lemon juice, salt, pepper, and Italian seasoning.
Close the Instant Pot lid. Pressure cook until the chicken gets tender.
Open the lid. Remove the chicken. Shred it with two forks. Put the chicken back in the pot.
Add the orzo. Turn on saute again. Cook until the orzo turns soft.
Taste the soup. Add more lemon if you want more bright flavor.
Spoon into bowls. Add parsley if you feel fancy.