If the HP desktop that you are using is similar to the All-in-One machines that I've supported in the past, then you may need to make a slight modification to your Grub file to disable ACPI warnings, which can keep a computer active.
Here's how you can do it:
- Open a Terminal (if it's not already open)
- Edit your
/etc/default/grub file with sudo:
sudo {editor of choice} /etc/default/grub
Note: Be sure to replace {editor of choice} with your editor of choice.
- Find the line that starts
GRUB_CMDLINE_LINUX_DEFAULT and add acpi=off to the end of the line, but inside the quotes. For example:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=off"
- Save the file and exit
- Update Grub:
sudo update-grub
Note: This step is important. If you skip it, then the change will not be applied no matter how many times you reboot.
- Restart your computer
Hopefully this allows your rest-deprived HP to shut down properly