I am running windows 8.1 pro on a Asus laptop
I have tried the following below and the power button still will not turn on in the Customize notification area on the taskbar.
Right-click on the clock by the notification area on the taskbar and select Customize Notification Icons.
In the Notification Area Icons window, check the Power option and make sure it is set to Show icon and notifications.
Click on Turn system icons on or off.
Set the Power option to On if not already set.
Click on OK to save the new settings.
If the above steps do not work to resolve the issue, try these next steps.
Open the Start Menu and in the Search field, type gpedit.msc and press Enter.
In the Local Group Policy Editor window, in the left navigation pane, expand User Configuration > Administrative Templates > Start Menu and Taskbar.
Find the Remove the battery meter option in the list on the right side of the window, right-click on the option, and select Edit.
In the window that opens, select Disabled and click OK to display the battery meter icon in the notification area on the taskbar.