Add olive oil to Instant Pot insert and turn on sauté function. Add the onion and cook, stirring, until softened. Turn off Instant Pot. Stir in the minced garlic. Add the diced green chilis, fire roasted diced tomatoes, enchilada sauce, chili powder, cumin, black beans and chicken broth. Stir well. Nestle the chicken into the mixture. Place the lid on and set it to the closed position. Turn the steam valve to the sealing position. Set the Instant Pot to manual/pressure cook, high pressure, for 9 minutes. When the cooking time is done, allow the pressure to release naturally for 10 minutes (this means just leave the Instant Pot alone for 10 minutes). Then, carefully turn the steam valve to the venting position to release the remaining pressure. Do this with the handle of a long spoon for safety. When the float valve drops down, the pressure has been released and it is safe to open your Instant Pot. Carefully remove the lid. Remove the chicken and shred. Return the shredded chicken back to the pot and stir in the corn. Season to taste with salt and pepper and serve with toppings as desired.
For serving: top with lime wedges, crumbled tortilla chips, sour cream or plain Greek yogurt, shredded cheese and/or avocado.