If Symantec Endpoint Protection (SEP) is installed on Windows 7 SP1, you may experience the following issues after upgrading to Windows 10 version 1809 (Windows 10 build 17763, AKA "Redstone 5" or RS5): inability to invoke the Start menu or other Taskbar Options like the Windows Button, Search Bar, and Edge -- process crashes.
This may occur particularly when SEP's ADC (Application and Device Control) component is installed.
Metro Apps fail to load Symantec's sysfer.dll (DLL for ADC) because the Windows upgrade process is not setting privilege group "ALL APPLICATION PACKAGES" for Symantec and other third-party modules.
When upgrading from Windows 7 to Windows 10, be sure to use the latest installation source. Or ensure that latest updates are downloaded during the process. This issue has been resolved in December 11, 2018 update KB4471332 from Microsoft. If no updates are installed during the upgrade, the issue described in this article will still occur.
If Windows has already been upgraded and is in a state where you are unable to invoke Start menu or other Taskbar options, you can implement the following work around
[Work Around 1]
Adding "ALL APPLICATION PACKAGES" default permissions to C:\Windows\System32\sysfer.dll and rebooting.
[Work Around 2]
Moving the SYSFER.DLL out of the System32 folder and copying it back. The copy and paste operation will replace permissions with those appropriate for the parent folder.
This will allow Windows to set the privilege automatically.