YOU SAID:

気づいなかった

INTO JAPANESE

気づいなかった

BACK INTO ENGLISH

I didn't notice

INTO JAPANESE

気付かなかった

BACK INTO ENGLISH

did not notice

INTO JAPANESE

気づかなかった

BACK INTO ENGLISH

I did not notice

INTO JAPANESE

私は気づかなかった

BACK INTO ENGLISH

I did not notice