Have you ever applied a cumulative update, CU, and the gray wizard, aka post setup configuration wizard or psconfiggui.exe, reports successful, yet the upgrade status page in central administration reports that it failed?
You can try running get-spproduct -local followed by a configuration cache clear on the farm and then another run of the gray wizard; but, chances are this weird behavior will still exist.
The thing that has worked for me in this case is the following powershell:
PSConfig.exe -cmd upgrade -inplace b2b -wait -force
and then when running that have the windows operating system services control panel (services.msc) open; so, that at step two of the four step process this command generates, you can have your finger on the start button for the World Wide Web Service on the server. When you get to step two, start the WWW service.
Now, if the command line run of psconfig says failed, go to the status page and check, I’ll bet it reports success. Really odd, and I am not sure what causes this, and neither the original fail nor the success are the tell all of whehter the farm is patched. You need to check the file system and compare the versions on the files to the versions in the csv file that you downloaded from the same page where you found information of the CU online.
Hope this little gem helps you the way it has helped me.