Place all of the ingredients in the Instant Pot. Mix everything so that the shrimp and the peppers are well coated in the fajita seasoning.
Cover with the lid, and make sure that the valve is in sealing position. Press on manual or pressure cook, and set the timer 0 minutes/low pressure. Once the cooking cycle has ended, do a quick release and serve over warm tortillas.
The bell peppers WILL become tender, so if you prefer crunchy peppers then only add them AFTER pressure cooking. Cover with the lid, and let them steam for a couple of minutes before serving.
You can either use fresh raw shrimp, or frozen raw shrimp. The difference between the 2 is that frozen shrimp will take longer to come to pressure so if you've added your bell peppers, then expect them to become really tender.
This recipe was tested in the 6 quart Instant Pot.