The harmony in general doesn't work as well as a professionally programmed product, but that being said we have to know more about how you have it connected before we can help.TV needs more time after power up before it will accept an input, but that only applies if you are using multiple inputs on the TV. If you're using the Marantz to switch your video the TV should stay on one input. Marantz needs very little time if any after power before will accept an input.

Just keep playing with it it may take you a few days but you'll eventually figure it out. Also an RF basestation will ensure commands are not missed as opposed to try to hold the remote still.