Greetings everyone. I am completely new on linux distribution. I have installed Kubuntu yesterday since then I am facing a peculiar problems. For example, when I go to 'Leave option' to turn off my pc and when I click the option it gets slept and I cannot turn it on again. It shows me the Lock screen, ant doesn't work any key. I am facing the same problem when I lock my screen. Any solutions. Thanks.

Which exact Kubuntu and Plasma version do you use? (see System Settings -> System Administration -> System Information)