I had a problem with my Harmony 360 and Momitsu V880DX DVD player where I couldn't get the DVD player to power on when starting up. The problem only seemed to arise when starting up from a power-off state--the DVD would miss the power-on command and I'd have to re-sync with Help. The problem did not occur when switching activites.

This situation usually indicates a problem with the delays. I tried increasing the Inter-Device delay substantially, with no success. In the process, I discovered what I think is a bug in the Harmony software--very high settings of interdevice delay (above about 4000 ms) seemed to disable the power-on command entirely--not only did it not work when starting an activity, but I couldn't even fix it with help. But it's hard for me to believe that the player really needs such a large interdevice delay, anyway. Working with the original DVD remote, I had no problem getting the DVD player to see a power-on command when delivered right after a command for another device. I also tried increasing the number of repeats to maximum, but that didn't help, either

What I ultimately did that seemed to solve the problem was tell the Harmony software that I needed different commands for on and off (even though the player has no discretes), and define the power-on command as Play followed by PowerToggle. Since the DVD player is off at that point, the initial Play does nothing, but apparently provides whatever little buffer the player needs to be able to see the PowerToggle command.