You said you are using the latest driver fro this wireless adapter, correct? Please tell us which drivers you have installed.
We also recommend that, if possible, try to connect to a different router with the same capability and see if you can connect to 5GHz.
I have the same problem with the same NUC. My router is a Netgear DGND3700V2 dual band wifi a/b/g/n (no ac). It has dual band and I have several other devices using 5 GHz wireless n with it including a laptop with an Intel AC7260 wifi card.
The NUC is brand new. I installed windows 64 bit 8 Pro then immediately did an upgrade to windows 64 bit 10 Pro obliterating all previous files. W10 is fully up to date. I have installed Wireless 18.30.0 PROSet 64 for Widows 10 and that version of the driver is showing in the properties.
Unable to see my 5GHz wifi network.
Go to BIOS click advanced/devices/onboard devices and make sure wifi dynamic regulatory solution is checked. My wifi card defaulted to another country Indonesia where I guess 5GHz is not allowed. Checking this box sets the wifi card to use local regulations which it holds in its firmware.