HP 27es monitor buttons not functioning correctly

[Creepton]

I have this problem with my HP 27es where I try to open the OSD menu using the menu button, and it will say "Power Button Locked" and after unlocking the power button, it does nothing. The button to the right of the power button actually turns off the display, after unlocking the power button, as well as the other to buttons to the right of it. The power button does nothing after the power button is unlocked. 

I have searched around the forums trying to find a solution to this problem and most of the times the solution doesn't work, or it involves using the menu, which I can't access.

This problem started happening after inactivity with the monitor for about two weeks. 

[Echo_Lake]

@Creepton
Thank you for posting on the HP Support Community.

I see that your experiencing issue with the HP monitor buttons not functioning correctly, 

Let's try:

Press and hold the MENU button for about 10 seconds, then release, then again try the instructions for doing a factory reset of the display.

Hope this helps! Keep me posted for further assistance.
If I have helped you resolve the issue, feel free to give me a virtual high-five by clicking the 'Thumbs Up' icon below, Followed by clicking on "Accept as solution" from the drop-down menu on the upper right corner,Thank you for posting in the HP Support Community.  Have a great day!

[Someone4]

I have the same problem. All of my buttons don't work. If I hold any of them down for more than 10 seconds I get a message saying Power button is locked. The only thing that seems to have any effect is I hold down the Auto Adjust or Input/Plus button. Then the monitor turns off but I have to hit the Auto Adjust to turn it back on.

Holding down the Menu button for 10 second causes a message to be displayed saying "Power button is locked", which changes to "Power Button is unlocked" after a few seconds. After that the buttons still don't work properly; the power button does nothing and Input/Plus button will turn the monitor off. To power back on, I have to press the Auto Adjustment button.

I've basically resorted to just pulling out the power cable. As far as I can recall it's been like this since I got the monitor but I used it so infrequently for the past two years that I never bothered to send much time with it. Now it's causing me headaches.

The level of documentation for this monitor on the Dell website is almost non-existent.

So unhappy with the monitor. Wouldn't recommend this to anyone.