Hi there. I recently upgraded my laptop to Plasma 5.5.5 (Kubuntu 16.04 LTS). The biggest problem is that the upgrade has broken power management. When I click on power management in system settings, I get a message telling me that the power management configuration module could not be loaded.
When I go over to Startup and Shutdown > Background Services, I can see that the power management service hasn't started. If I try to start it, I get two error messages in different windows:

1. Impossible to launch the service powerdevil. Error: Message recipient disconnected from message bus without replying
2. I also get a crashed application window from a segmentation fault in either kded5 or kdeinit5 (sometimes it's one, sometimes the other).

I've looked through this already but it hasn't helped much : https://forums.opensuse.org/showthread. ... -be-loaded

I've checked and upowerd is running
I tried "kbuildsycoca5 --noincremental" and rebooting but it had no effect.

I'd be grateful for any help!

Ok, fixed it myself. Turned out to be a package version problem and an update to Plasma 5.6.5 resolved it.