For some reason when I turned on my 2 week old NUC6i5SYH yesterday it refused to connect to the internet via ethernet connection. It has been fine since I got it and I have made sure that all the Intel Drivers that should be updated have been. I set up the WiFi (which I hadn't bothered to do) and that worked fine - went through all Drivers again updating as I go - only thing I didn't get to look for was any BIOS updates.
I eventually checked the cable (fine) then I checked my switch (fine) and finally my hated SKY router (as 'fine' as normal). Plugging my laptop into the same ethernet cable demonstrated that my laptop immediately switched to a cabled connection - so I now know it's either software or hardware playing up with my NUC.
My plan tonight is to delete the ethernet network drivers in Device Manager (I'm on Win10 currently) and to reinstall them - then if necessary investigate any BIOS updates.
What else am I missing? it seems pretty certain that it's the NUC as everything else tests ok, but why suddenly stop working overnight between uses? In the Visual BIOS currently on it - it shows that LAN is switched ON.....
I'm puzzled and annoyed. Any help would be appreciated.
I experienced the very same problem. I went through the same procedures as you did, and it took me some time to solve it:
The ethernet adapter ind the NUC6I5SYH is the "Intel I219V Gigabit Ethernet LAN adapter". Yesterday Intel released the new driver-pack to the "Intel® Ethernet Connection I219-V", and you find it here: http://ark.intel.com/products/82186/Intel-Ethernet-Connection-I219-V# @downloads Intel® Ethernet Connection I219-V Specifications
I have used the latest version 20/7, and it solved the problems.
You're are probably aware of it, but download the driver, un-zip the compressed files, open the Windows Device manager and update the ethernet-driver pointing to the folder containing the downloaded driver.
Have fun - Trowin