I'm using fedora OS. It was working properly until the message "the system requires an update, install updates" was shown. I clicked "install updates" to start the installation but even though it began fine it suddenly stopped at the 55% mark, and I then restarted the laptop. The result is that the OS wont boot, stopping at the logo interface.
Reboot, but right as it starts to boot hit the 'esc' key to disable the splash screen (the fancy animation you see). This will drop show you the commands being run and help identify the issue.
A couple of notes about the software app:
I find it to be very hit or miss. It doesn't show all packages available and it doesn't really provide any information as to what it is doing when it is working. Use yumex (included in a standard install) if you want a graphical package manager, or dnf on the command line for the best results and least errors.
Also, I believe that updates are installed either as the machine is powering off or as it is powering up. I forget which one, but this also caused me some alarm as it appears that the computer hangs.