Hello Intel888, I am sorry to hear you are having problems with your NUC and the AC7260 adapter.
First of all, I need to know which is the current BIOS version installed on your system? Please provide me with this information as soon as you can.
Could you test the Wireless adapter on another computer, in order to discard if it is defective?
It looks like the error code 28 is related to the chipset driver. So you could try to reinstall it again. Download Center