Add steel cut oats in Instant Pot. Add in cold milk, water, pumpkin puree, pumpkin spice mix, salt, vanilla, and maple syrup.
Mix everything well and make sure all the steel cut oats are submerged in the liquid. Close lid and pressure cook at High Pressure for 10 minutes.
After 10 minutes, let the pressure release naturally for 5 minutes and then quick release the remaining pressure. Open the lid carefully.
The steel cut oats will look watery when you first open the lid. Give it a few quick stirs with a spatula to combine and thicken the steel cut oats.