I have a similar issue but cannot download the Cleanwipe tool without a serial number. We received serialized versions though the university I work for through a license agreement, but I don't have a record of my serial number since I uninstalled it quite some time ago.
Trying to run the critical Windows update mentioned, and receive the error about it can proceed without Endpoint uninstall. I've called Symantec, but no one would help me without a serial number.
My laptop was originally a Windows 7 machine that I upgraded to Windows 10 over a year ago, so going back to the factory install would take me all the way back to Windows 7.
Anyway I can move forward, and get Endpoint off my computer?
Thanks,
Ron Conrad