Combine first 4 ingredients in a large bowl and stir to combine.
Turn Instant Pot on to saute and saute the onion and celery together with the butter for 2-3 minutes. Add in the seasonings and continue sauteing for another minute.
Add the sauted mixture to the cubed stuffing. Stir to combine. Transfer into a metal Instant Pot pan, such as a stackable pan set (in this case you’d be able to cook two sides at once). Cover pan with lid or foil.
Add 1 ½ cups of water to the inner pot of the Instant Pot. Lower the pan with the stuffing in to the inner pot on a trivet.
Close the Instant Pot lid and turn pressure valve to seal. Cook on manual high pressure for 20 minutes.