Q. Can I perform an in-place upgrade from Windows 7/8.1 to Windows 10 LTSB?
A. No. This is not supported. While it worked to the 2015 Windows 10 LTSB it was never supported and it is explicitly blocked to the 2016 Windows 10 LTSB. This is documented in the supported upgrade paths to Windows 10 at https://technet.microsoft.com/en-us/itpro/windows/deploy/windows-10-upgrade-paths.