I have a NUC7i5BNK that will not read any USB 3.0 flash drive. Thinking it was driver related, I did a full sweep of BIOS and driver updates, but had no luck. Even upgraded Windows 10 from 1709 -> 1803. I tried booting from it, but the BIOS wouldn't even see it as a bootable device, which is when I realized this was probably hardware related. Note that this same flash drive works fine on multiple other PCs (including a Windows 7 laptop using either USB 2.0 or 3.0 ports, and another Windows 10 PC using either USB 2.0 or 3.0 ports). This flash drive also works as a music storage device for my car. So the issue is definitely not with the flash drive.
After researching on these forums and other locations, I found a suggestion where using a non-USB 3.0 extension cord to connect the flash drive worked around the problem. Sure enough, that worked around the problem for me. Most of the posts I found were related to older NUC models. Is this a known issue?
Windows 10 Pro 1803
USB drive: PNY PRO Elite USB 3.0 512 GB (P-FD512PRO-GE )
This is not an isolated issue, nor is it unique to the Intel NUC line. After I posted this I had just purchased a 2nd Intel NUC for another project, which is the same make and model of my other NUC. Both have the same issue. I was also recently building another computer that has a Gigabyte motherboard with the H170 chipset. This board has the exact same problem. For all 3 computers, if I directly connect my flash drive to any USB port, the system will not recognize it. I have to connect my flash drive to a USB 2.0 extension cable for the BIOS to see it and to be able to boot from it. This is a larger problem than the NUC, so I'm not going to bother troubleshooting further.