"Do you want those shirts?"
Translation:¿Ustedes quieren aquellas camisas?
It isn't wrong anymore. I type exactly that and it was accepted.
Perhaps you had a typo. When duo notices your sentence is wrong, it seems it will give you its expected answer, not the closest correct answer. If you had some small typo (e.g. "¿Quieres esas camisa?") it will often tell you it wanted "¿Ustedes quieren aquellas camisas?" and say you used the wrong words, even though the real error was something else entirely (e.g. "camisa" vs. "camisas").