Well that didn't work!

From the system recovery screen I selected "apply update from ADB" from my PC I ran "adb sideload lenovo.tar.gz"

It gets up to 100% on the PC no problems, but then comes up with "Installation Aborted" on the tablet.

It's a Lenovo A7600 that got killed by a firmware update, I'm trying to load Android 4.4.2 from Lenovo website

Any clues?