Two lessons ago i encountered "¿Ustedes disfrutaron la playa?" - so why does the verb come first here, but second in that example?
It doesn't make a lot of difference where you place the subject pronoun in a yes-or-no question. "¿Ustedes disfrutaron la playa?" sounds like we're focussing on the people: "Did you, specifically, enjoy the beach?" In the sentence "¿Disfrutaron ustedes sus vacaciones?" it sounds less emphasised, maybe more clarifying that I'm talking to "you" instead of "them". But the difference is small and the precise meaning can be modulated by which word you emphasise when speaking.
"las vacaciónes" was rejected in favor of "sus vacaciones" But the coaching statement did not seem to be helpful. It stated: "vacaciones" is plural, not feminine. However, it is both plural and feminine. The real problem seems to be the use of the definite article "las" instead of the possessive "sus".
I tried " did all of you enjoy your vacation" and was rejected. I have been told that we need to honor regional variations which is a good thing. I does not help me learn Spanish when all of the examples use a regional variation foreign to a lot of English speakers. Would you translate "all of you" into ustedes or not when they say it is wrong. If "all of you" is not ustedes there is no translation for ustedes in my region which includes several countries.