If you want to quickly fix this issue you should change kdmrc file.
There is a line
HaltCmd=/sbin/shutdown -p now
It should be changed into
HaltCmd=/sbin/shutdown -P now
There is another way to do this is. You can make this through System Settings > Login Screen. On Shutdown tab you can change Halt command from /sbin/shutdown -p now to /sbin/shutdown -P now.
If you want to quickly fix this issue you should change kdmrc file. /sbin/shutdown -p now /sbin/shutdown -P now
There is a line
HaltCmd=
It should be changed into
HaltCmd=
There is another way to do this is. You can make this through System Settings > Login Screen. On Shutdown tab you can change Halt command from /sbin/shutdown -p now to /sbin/shutdown -P now.
After that you should reboot your computer.