We just replaced the valve body on my 2018 Nissan Rogue. We were told sometimes they have to be re-programmed sometimes not. My question is, how do I know? At this point I’m assuming I don’t since there are no codes and it’s driving fine, but just in case, what issues are there when it does have to be reprogrammed. Thank you.

There's no ROM in the VB on the gen2, I think the reason Nissan recommends reprogramming is to get rid of any "unerasable" DTC's like P17F1 that only go away with a TCM repro. I'll double-check at the shop later today, but I'm pretty sure DTC's are the only issue and you shouldn't need a repro if there are none.

The only DTC we have right now is a motor one which is the upstream O2 sensor. I have that on order. It should be here tomorrow. But so far there aren’t any transmission codes.

There should have been a CD that came with the new VB, plus a new QR sticker to identify it. You can get both of those from Nissan based on the VB serial number if they didn't come with the VB (assuming the VB was an OEM part). It's probably fine for the short term, but even though there are no DTC's, you might be doing the tranny long term damage from over- or under-pressures if you leave it the way it is without a repro.

Yes its OEM and did come with CD. I guess I’ll go ahead and take it to the dealer for reprogramming just to be safe. Thank you very much!

You're most welcome. Happy motoring!

Thank you. Since you seem to be real knowledgeable in this area, let me ask you one more question. For the past year we’ve had an issue where my car will sputter and die when I press the gas. The problem got better when we started using higher octane gas but will still do it every now and then but not near as often. The only code we have is the O2 sensor and my husband said that is unlikely the cause. He is thinking fuel pump but that’s in the gas tank and a major undertaking and apparently there’s no fuel filter on this car. Husband also said typically when a fuel pump goes out it just goes, it doesn’t do what this car is doing. Do you have any experience with this, or know what might possibly be causing it? Thank you!

Fuel pumps do go in-and-out sometimes, but not usually the way you're describing. Intermittent no-starts are the common system for that, from the fuel pump spinning up slowly or not at all. Dying or stumbling intermittently when you hit the gas has five common causes:
1) Bad brake switch - The TCM monitors the brake lamp circuit and won't let the car accelerate if the lamps are lit. If your stumbles are occurring when coming off stoplights, a sticky switch is a likely culprit.
2) Dirty throttle body - Easy to clean with intake cleaner and a toothbrush, but don't force the throttle plate open by hand. Turn the key on and brick the gas pedal so the ECM holds the plate open for you. Pay most attention to the bottom edge and bottom-back section of the plate, that's where crud builds up.
3) Bad, dirty, or miscalbrated MAF - They rarely go bad, suspect that last. They get dirty or out-of-calibration all the time. Easy to take loose and clean, two phillips screws. Use intake cleaner or MAF cleaner, you don't want to leave any residue. After cleaning both the MAF and Throttle Body, do an IAVL (Idle Air Volume Learn). CVTz50 has that capability if you enable "Experimental Features" in the main settings. Great feature, I use it all the time because it's way faster than Consult3+. IAVL recalibrates the relationship between the MAF and throttle plate in the ECM's memory.
4) Crummy PCV Valve - Very overlooked, but sticky PCV's cause all kinds of weird issues because they affect the intake stream and manifold vacuum. Not worth cleaning, just replace it.
5) Crank and Cam Sensors - If you can't find any other cause, CKP's and CMP's are often the culprit. They can get weak but not fail completely, and because reluctance (magnetic flux) of the tone wheels increases with engine speed, they often malfunction only at low speeds and cause no codes.
In this case, since you just changed VB's, I'd give it a few miles to see if the VB also fixed the stumble. It's entirely possible for an unresponsive valve in the tranny to stall the car or cause major stumbles.

Great! Again thank you very much