Dell Latitude 5175 power button not working! (can't enter sleep mode/hibernation, etc by pressing power button)

hg87590705,

Does the system hibernate or enter sleep mode when you close the lid?  Click the link below for information that may help you resolve hibernation

Using Windows 10 Sleep And Hibernation Settings 

No, I don't own a keyboard dock to test but I think that would probably put the device to sleep.

You see, there is no problem with sleep mode itself; I can still enter sleep mode via start menu -> power icon -> sleep. I think the problem's to do with my windows not being able to detect or recognize that there is a power button..  even key mapping programs were unable to pick up any input signal when the power button was being pressed.

hg87590705,

There is a setting in the bios for the keys. It is listed under the Secure Boot Heading and then Expert Key Management. 

While in the bios navigate to the Performance sections and the C-States Control and verify there is a checkmark in the box. 

Save the Changes and Exit.

Could you please expand on that?

I managed to find Expert Key management but have no clue as to what to do next.

At first I figured pressing "Reset All Keys"  would fix the problem.

Instead it took me to bitlocker recovery and had me enter a security code to boot to windows, and even after all that my power button still did not work.

What do PK, KEK, db, dbx all mean, and what do I have to do in order to fix my power button?

Oh, and my C-States Control had already been check-marked.

 I recently ran into the same problem and was finally able to resolve it by installing the Intel HID Filter Driver from the Dell 5175 support site. It's older than whatever version was installed on my machine (maybe via a Windows "Update"?) but it restored the expected behavior of the power button.

Thank you for sharing this hint! It helped saving my computer

Describing symptoms and solution here for reference, because the connection is not obvious:

Symptoms were:
Dell Latitude 7250 would not start after pressing power button. (Before, battery had run flat in suspend mode) The recommended workaround of removing battery, draining remaining energy by pressing power for some seconds, then repower and retry did not work. However, system was booting when connecting power supply while battery removed. While system was switched on, it operated normally, but had no reaction to the power switch (not even switching to suspend.)

Solution was:
Enter Bios Settings =>  Secure Boot => Expert Key Management:
Set "Enable Custom Mode" to on, was off before.
Custom Mode Key Management is kept to PK.

Thereafter, power button worked again!