Set Instant Pot to sauté for 10 minutes and allow to preheat.
Add oil to pot, and add chicken and brown on each side, about 1-2 minutes on each side. Remove chicken and set aside.
Add onion to pot and sauté until edges turn translucent, about 10 minutes. Add garlic and sauté for another 30 seconds.
Add chicken, 1 Cup enchilada sauce, corn and black beans to pot. Place lid on pot and set to manual for 10 minutes if using thighs, 6 minutes if using breasts.
While pot is cooking, heat a large skillet over medium heat. Cook tortillas in batches, remove when they just begin to brown.
Release valve on pot and remove chicken from sauce. If sauce is too thin, you can continue to cook on sauté until it thickens to its desired consistency.
Remove sauce from the instant pot to its own bowl, and stir in yogurt.
Shred chicken and begin assembling stacks by adding cheese, chicken, and sauce to each tortilla layer. Garnish each top tortilla with cheese, lettuce, and tomato, and serve.