Problem
Bob's El Capitan is showing installed in MSU, but his computer is still on Yosemite.
Solution
First, promote yourself to be admin on the computer by running CIAS APD located in your Utilities Folder
Once admin, launch the terminal application
In the terminal window, type the following command
sudo pkgutil --forget com.googlecode.munki.installosx.pkg
Hit enter and then close terminal
Launch Managed Software Center application again and check for updates
The OS X update you were trying to install should now be available again
If the update continues failing on installation, please submit a Help Desk ticket stating that.
