You don't provide enough information for anyone to be able to help you. I only speak for myself (I am sure there are at least a few others similar to me) but I have no clue what an Arduino Mega is... or an Arduino Ultra Mega... or an Arduino Ultra Ultra Super Mega. I don't intuitively know what the ON LED or L LED is and how it figures into the schematic. For example, if the ON LED is tied to the power supply and simply indicates there is voltage then you probably have a significant problem (no wall adapter attached, failed voltage regulator, etc.).
Let's assume it's a problem with your code. When problems like this occur you should really step back and start simple. Write the simplest bit of code that you can to toggle a pin. Just the bare minimum code. Don't include anything that's not necessary for toggling that pin. Does it toggle? If so, you know your micro is running. Now, progressively introduce features which you recently changed (before it stopped working) and continue to test them incrementally.
The more information you provide the better someone can help you. The above is my best advice until you can edit your original question with more detail.