Add the cream cheese to the mixing bowl. Using the electric mixer lightly beat the cream cheese. Slowly add in the eggs, sugar, rum extract, nutmeg, cinnamon, salt, and cornstarch. Lightly beat to only combine. (Don't over mix)
Scrap the sides of the bowl with the rubber spatula.
Slowly add in the eggnog. Mix only until the batter is smooth. (Don't over mix)
Slowly add the mixture onto the crust.
Release any larger air bubbles by gently tapping the pan on the counter.
Pour 1 cup of cold water in the Instant Pot. Put the wire rack in the bottom of the pot.
Position the tinfoil sling around the pan. Carefully lower the pan into the Instant Pot. Secure the lid. Set the pressure release to close.
Cook for 29 minutes on manual high pressure. As the timer beeps turn the Instant Pot off. Let the cheesecake to natural release. Cool without manually releasing pressure. (This will take about 10-20 minutes)
Open the lid carefully once the pressure has released. Be careful so that condensation will not drip on the cheesecake.
If needed carefully use a paper towel to dab any moisture/liquid that may be on the top of the cheesecake.
Remove the cheesecake from the Instant Pot.
Move the cheesecake to cool to room temp on a wire rack.
Transfer to the refrigerator for 2-4 hours. (This will help the cheesecake to firm up.)