YOU SAID:

he told he couldn't come to the party tonight

INTO JAPANESE

彼は今夜パーティーに来ることができないと言った

BACK INTO ENGLISH

He said he couldn't come to the party tonight

INTO JAPANESE

彼は今夜パーティーに来ることができなかったと言った

BACK INTO ENGLISH

He said he couldn't come to the party tonight