Which sentence is the correct one?
1)you didn*t be in the party yesterday
2)you didn*t were in the party yesterday
3)you weren*t  in the party yesterday

The correct sentence (верное предложение):
3) you weren*t in the party yesterday - глагол to be (were) сильный, он не может использоваться со вспомогательным глаголом did (а также с do и does)