Yup both dos and efi tools fail with similar errors (I don't recall the exact wording but basically they can't communicate with the ME).

I had the mini-pc apart earlier to solder in a sim card connector (I'm planning to add a 3g or 4g mini pcie card) so whilst I had it apart I did some more testing).

I flashed the bios from an i5 Broadwell based MSI Cubi (similar chipset) using my trusty external flash programmer (I know this is seriously NOT recommended but I figured what the hell, I can always flash back) just to see if the ME was detected using that full bios flash.
Surprisingly the system boots up nicely with the MSI bios and boots into windows with no issues at all - BUT - sadly still no ME detected so I flashed back to the correct bios image and gave up.

I now fear that ME is actually hardware disabled via the motherboard on this mini-pc and not via the bios. My suspicion is that there is most likely a bridged (or open) pair of solder pads somewhere on the motherboard that would normally contain a jumper to enable or disable ME. At this point I think it's a dead end as I can't start randomly opening and closing motherboard solder joints hoping to get lucky (well I could, but I won't because I don't like the smell of smouldering burnt electronics).

I'm stubborn enough to have a look the next time I have it apart - If aint broken fix it until it is right? lol