I think "off" and "on" and "on/off" (normal toggle mode) are actually separate codes; you may have used the "off" code.
Yamahas are squirrelly for IR codes. 99% of programmed uni remotes do not have many of the Yamaha codes, for whatever reason. The only way I ever replaced my circa 1990 RX-100u remote when it failed was with a RatShack Karma remote, and that only worked because you can call an 800 number, tell the person what codes you are missing, and then they will have you hold the remote up to the phone and program it for you over the phone (a neat piece of analog '90s technology).
Remote code questions are best answered at Remote-Central.com. If that doesn't work PM Edmund on that forum; In 10 years I have never seen a question he can't answer. He might also live on this forum under that name.