BTW, moderators, this is a regular issue, and will continue to be for the forseeable future, as it is not at all obvious that anything USB connected via the OTG cable needs this hidden setting activating. This also works quite differently to other manufacturer's implementation of OTG connectivity, and even differently than many previous Xperia devices (my XZ & XZ Tablet don't require this). I suspect it has been (reasonably) done by Sony to reduce power consumption, as the phone or tablet does not have to keep checking the USB port to see if an OTG device has been connected.
Is there any chance of haveing a sticky explaining briefly how to connect a USB OTG device, for both the ZX3+ and Z4 Tablet lists here (I own both, and it works the same for both devices). This would save a lot of extra questions...
