I found this “ERROR: Windows SDK v8.1 must be installed in order to build this target”
Which I assume means that you don’t have that SDK is not installed, I think you have to rerun the VS installer to get that; But am not sure as I have never had to do that before.
Could you try packaging for Win32?
I had an issue packaging for Win32 recently, But not for Win64 (It had something to do with an actor that I placed in a level that seamed to have a reference to another actor where it was complaining that a attached component was not really attached)
HTH
–Edit–
There is a section in the log telling you to check another log file, That one seams to have a higher logging verbosity.
Search for the string/text “See logfile for details:”
Which is stored here “C:\Users<USER_NAME>\AppData\Roaming\Unreal Engine\AutomationTool\Logs<ENGINE_VERSION>”