Why doesn't OrCAD show zero voltage here and can I fix it?
Bob Pease would approve of this exercise...
What's all this Spicey stuff anyhow?
Expecting perfect output from a simulator using numerical methods is just not realistic : and placing absolute trust in SPICE simulations (which are models of analog reality, not reality itself) is a serious mistake.
When you have finished this exercise you will understand...
Present your pencil and paper answer as the exact solution; and present the fact that your simulation is in very close agreement with it as supporting evidence.
And just for fun, calculate what precision of resistors you would need to build this and get less than 10 pV error. Then try to find those resistors for sale online...
Or change just one of those resistors by the smallest tolerance you can find, and re-simulate. Notice how far off the result is now, compared with the rounding error.
In real life, sometimes you need better supporting evidence in physical form... again from the legendary Robert Pease.

(not Bob Pease, but one of his prototype : the very first LM317 linear regulator!)