YOU SAID:

what is a party I've never been

INTO JAPANESE

私が今までになかったパーティーは何ですか？

BACK INTO ENGLISH

What was the party I had never had before?

INTO JAPANESE

私がかつて持っていなかったパーティーは何でしたか？

BACK INTO ENGLISH

What was the party that I had not had before?

INTO JAPANESE

私が以前に持っていなかったパーティは何でしたか？

BACK INTO ENGLISH

What was the party I did not have before?

INTO JAPANESE

私が以前に持っていなかったパーティーは何でしたか？

BACK INTO ENGLISH

What was the party I did not have before?