YOU SAID:
I couldn't be happier about the new baby
INTO JAPANESE
私は新しい赤ちゃんに満足できなかった
BACK INTO ENGLISH
I was not happy with the new baby
INTO JAPANESE
私は新しい赤ちゃんに満足していませんでした
BACK INTO ENGLISH
I was not happy with the new baby
That didn't even make that much sense in English.