If You Downgraded Back to the Original Installation After Upgrading to 15.5

Look here to learn what to do if you upgraded to Adaptive Server 15.5, then downgraded back to the original version.

Restore the original messages by running the following script after downgrading the server. 
isql -Usa -P<sa-password> -irestoremsgs.ebf
Parent topic: Downgrading from Adaptive Server 15.5