none of the suggested solutions will work until the cause of 0x80240020 is solved. according to M$ this error means :
WU_E_NO_INTERACTIVE_USER Operation did not complete because there is no logged-on interactive user. (
https://support.microsoft.com/en-us/kb/938205 )
Why there needs to be an interactive user is, is a mystery to me.
according to MSDN an interactive user is:
The interactive user is the user that is currently logged on to the computer where the COM server is running. If the identity is set to be the
interactive user, all clients use the same instance of the server if the server registers its class factory as multi-use.
https://msdn.microsoft.com/en-us/library/windows/desktop/ms686587%28v=VS.85%29.aspx?f=255&MSPPError=-2147217396
but this still doesn't explain why windows 7 updates, which is ables to pickup and install all other updates, is failing to install the "Upgrade to Windows 10 Pro" update.
maybe adding the current user to the "Distributed COM users" group might do it.
"Distributed COM Users" group description: Members are allowed to launch, activate and use Distributed COM objects on this machine.