YOU SAID:

robin was not that happy since it

INTO JAPANESE

ロビンはそれ以来、それほど幸せではなかった

BACK INTO ENGLISH

Robin hasn't been so happy since

INTO JAPANESE

ロビンはそれ以来とても幸せではない

BACK INTO ENGLISH

Robin hasn't been very happy since.

INTO JAPANESE

ロビンはそれ以来あまり幸せではありません。

BACK INTO ENGLISH

Robin hasn't been very happy since.