Cannot detect arduino leonardo on device manager

Hello All, I am newby to this forum. I connect arduino leonardo to PC win7 x86_64, however it cannot be detected on device manager. The L LED and ON LED are continuously ON. I try different USB port and cable, it has same problem. I push the reset button but the two LEDs still on. Do I have to install specific driver before connect to PC?

I install the arduino environment but the problem still appear. I connect to my Macbook Air also and it did't have any notification of USB connected to the board.

It seems that the Arduino Leonardo has 5V power but is not running. You might want to try to burn the bootloader, but perhaps something is broken :(

Is it an official Arduino Leonardo ?

To burn a bootloader, you need a programmer or "Arduino as ISP". It is for advanced users, but sometimes it helps.

Thank you for your reply. I integrated the board with additional ADC chip, transistor and Op-amp. I will try Arduino as ISP..