Place the chicken breasts inside the Instant Pot. Season with 1 teaspoon salt, 1/2 teaspoon pepper and garlic powder. Pour the water around the chicken.
Close and lock the lid. Set the pressure release valve to the sealing position.
Cook on high pressure for 8 minutes. Allow for a 5-minute natural pressure release, then release any remaining pressure.
Carefully open and remove the lid. Check the internal temperature of the chicken to ensure it’s reached 165°F(75°C) or higher. If not, seal and cook for an additional 2 minutes.
Transfer the chicken to a cutting board. Using two forks, shred the chicken.
Pour out all but one cup of the liquid in the pot.
Return the shredded chicken to the pot. Scatter the bell peppers and onion on top. Sprinkle on the remaining salt and pepper, chili powder, cumin, and paprika. Don’t stir.
Close and lock the lid. Pressure cook on high for 2 minutes, followed by a natural pressure release. Stir the contents of the pot.
Heat the tortillas until pliable. Serve the fajitas in the flour tortillas.