The failure mode is tone. The same five words can read as a genuine request for help or as sarcasm, and only delivery separates them. Voss pairs every calibrated question with tactical empathy for that reason, which is the technique the question sits on top of.
The second failure is repetition. Ask How am I supposed to do that three times in one meeting and your counterpart stops hearing a question and starts hearing a tactic. Once it reads as a script, the effect inverts.
There is a third case worth naming. Some negotiations have no hidden information left to find, and both sides know the terms. A calibrated question there only adds a turn to a conversation that could have closed.
The first line is the one worth rehearsing. Voss's tactical empathy is the layer that makes the delivery land, and running the questions without it produces the sarcasm failure on the first try.