Since your password is encrypted - you need to use the -X option.
initiates the login connection to the server with
client-side password encryption. -X enables
both extended password encrypted connections and password encrypted
connections without plain text password reconnection. isql (the client) specifies
to the server that password encryption is desired. The server sends
back an encryption key, which isql uses
to encrypt your password, and the server uses the key to authenticate
your password when it arrives.