First of all this is in WRONG SECTION, you have to ask this in Q&A, some Mod probably will have to move it.
BTW, after push power button you got a windows with 3 options: Power Off, Airplane, Screenshot, right?
Then you click on Power Off and it do not power off because another Windows should pop up with Cancel or OK to confirm that.
Do you get that option? Try again...
IF I HELPED DO NOT SAY THANKS, CLICK IT.
My Evolution: Sony Xperia Z1 - UB + 4.3 Rooted + Deodexed, HTC HD2, HTC Diamond 2, HTC HD Blackstone, Nokia 7070 Prism, Qtek 9100, Nokia 3100, Motorola T720i, Nokia 3310, Sony Ericson PF 768 (Blue)
How Get Root on Sony Xperia Z1 with Locked Bootloader and the Latest Android 4.4