Breakdown of Nie powinnaś była zignorować jego wiadomości.
być
to be
nie
no / not
powinien
should, ought to
jego
his, its
Questions & Answers about Nie powinnaś była zignorować jego wiadomości.
Why do we use była here if powinnaś already translates to "you should"?
While powinnaś looks a bit like a past tense verb because of its ending, it functions as a present tense modal meaning "you should". To express a past unfulfilled obligation—something you should have done or should not have done—you must add the third-person past tense form of być (to be) that matches the subject's gender. Here, it's powinnaś była (you [female] shouldn't have).
Why does powinnaś have the -ś ending while była does not?
In this specific "should have" construction, the personal ending (here, -ś for the second person "you") attaches to the modal word (powinna), while the auxiliary verb (była) stays in the third person. It is always powinnaś była, never powinna byłaś.
Why is wiadomości in the genitive case instead of the accusative?
This is the Genitive of Negation in action. Even though the negative word nie is attached to the modal verb (powinnaś) and not directly to the main verb (zignorować), the entire action is negated. Since zignorować normally takes a direct object in the accusative (wiadomość), negating the sentence forces that object into the genitive case (wiadomości).
Could I use the imperfective verb ignorować instead of here?