I have a Harmony 550 and older 50" Panasonic plasma (2004 year). The Panasonic remote only has a power toggle, but I found discrete on/off commands for the TV among the device commands and can use those to program my activities.

The problem is that while the discrete "off" works, the discrete "on" command does not. Any ideas on how I can get a functioning discrete "on" command in my remote?

Why not just use the Power Toggle for the "discrete on"? This way, it should still turn off with the discrete off and should turn on every time.

I had an Panasonic HDTV (CRT) that only worked with the Power Toggle.

Yup - that's how I have it set up now, it's just much more stable when using discrete on/off commands. Using the toggle, devices can get out of sync and the remote will turn the TV off is it's on when it thinks it's off, etc.

I can manage it, but it's not wife/kid/grandparent proof. I believe the discretes are highly preferable when available, it's just that for some reason the discrete on that Logitech provides for my TV does not work.