D2719HGF, cannot unlock power button

Hi all,

I have a D2719HGF monitor. My power button has locked I do not know why I had not touched the power button when it occurred. I tried unlocking the power button by holding it for 10-15 seconds. That did not work. I tried unplugging the power cord as well as any other cords plugged in, I pressed and held the power button while the monitor was completely unplugged for 40 seconds then pressed the button again. This did not work either. I am able to lock and unlock the OSD by holding the "ENTER" button on my monitor but I am not able to unlock my power button.