WOL from S5 i5 NUC - cannot get it to work, but S3 does ?

Hi guys

New to the NUC scene and trying to get WOL from completely switched off (S5?) state to work and having problems.

Running Windows 10 on it, but I figured the OS is irrelevant since the box is being woken from an off state where no OS is in play, but some posts I've read kind of indicate that the OS has a bearing on this stuff.  Can someone explain why that would be the case ??

Anyway, I can get the computer to wake from a suspend state using WOL but not from an off state, S5.

When I tick the Wake from S5 in Bios it expects a date and time, but I just want to do it on demand, surely that's doable ?

Tried ticking and unticking the Deep S4/S5 checkbox - no difference.

Baffled.

Anyone?

Thanks a lot

Scott