I need help

If you plug in everything one by one, does it still do the same? For example, just have the controller and mouse. After, try controller and keyboard.

What is the make and model of your mouse and keyboard?

If you plug in your controller directly to your console, does it power on by itself or do you need to press the home button to power on?

Also, are you using the power port on the unit (connect to an outlet)?

Did you try connecting the K2 with the controller only and see if the controller turns on? If the controller (and K/M) turn on briefly and shut off or do not turn on it is an indication that either the keyboard and mouse are consuming too much power, or either the keyboard or mouse (or possibly both) are not compatible.

Start by connecting only controller to K2 and see if it turns on normally, then connect mouse, then keyboard. You will see at what point it fails. If it fails at the keyboard, remove the keyboard and mouse then swap the turn on order to plug in keyboard first and retry. If it dies after connecting the keyboard you can add a 2A or greater power supply to the K2 Power port and try again. If that doesn't solve the issue it is a compatibility issue and needs a different keyboard.