Combine vegetable stock, rice, mushrooms, garlic, carrots, celery, sweet potatoes, onion, bay leaf, and seasoning in an instant pot pressure cooker. Stir gently until all ingredients are well mixed.
Cover and cook on manual, high pressure for around 20 minutes. After, naturally release the pressure for 10 minutes. Then gently open the vent, quick release the remaining pressure, and remove the lid.
Discard the bay leaf and add coconut milk and spinach to the soup. Stir gently until all the ingredients are combined—season with salt and pepper. Serve hot.