In Service Orders (or appointment's) I have found that when I add an item that has a new stock item + warehouse combination the Item Warehouse Detail for the new warehouse is not added to the stock item..
This is causing it to not appear on my Prepare Replenishment screen.
If I manually add the warehouse detail to the stock item, I will have to also have toggle the Override Replenishment Settings for the Replenishment Source & Replenishment Warehouse to load from the defaults outlined on the Stock Items screen.
I hope this makes sense, I can provide screen shots if needed for more explanation.
Acumatica 2023R2 Build 23.212.0024