I don't know about bloggers/reviewers, but a quick search on that specific model says that although the memory has been tested at 1.35v, the SPD Voltage is 1.5
If so that could be the problem. Another common problem is memory "density" - if you can see 8 chips on each side of the module (instead of 4 chips on each side) then the density might not be compatible with the NUC.
I have a NUC5i7 and use 16gb of Crucial SO-DIMM DDR3 PC3-14900 Unbuffered NON-ECC 1.35V In English, that's low profile memory running at 1866 gigahertz designed to work with laptops and SFF's like the NUC series. Intel has shipped NUC5i7's loaded with similar memory for reviewers. and, Crucial indicates this memory is compatible with nuc5i5 motherboards as well. As Dougho has mentioned aside from the speed, it's critical that the memory you choose meet the specs Intel has set out. It's mandatory that the memory be rated to operate at 1.35 volts.
The best way to avoid mishaps and ensure that your memory is compatible with your box is to use the memory manufacturer's configurator or scanner apps. These are very useful. While Intel doesn't try to test all the memory out there in all its products, the manufacturers do try to test their products against all the motherboards of major manufacturers, like Intel. After all, they want to reach the widest customer base and sell what they are making with no complaints! The scanner/configurator/advisor apps can found at every memory maker's web site.
For clarification: I said Corsair's SPD Voltage is 1.5 and other reply mentioned rated to operate at 1.35 volts. A post a few months ago on an ASUS forum also mentioned such issue with this memory. What we are trying to say is that while Corsair might test their memory at lower voltage, Corsair did not write that lower voltage into the SPD (Serial Presence Detect) which is the standardized place that computers read necessary information about how to use the memory. So the NUC reads "1.5" and starts blinking incompatible memory (even though Corsair might say that if they just proceeded supplying only 1.35 it would be good enough). If someone says same part number worked on their NUC, perhaps Corsair revised the SPD programming sometime and you might have "old" version while they might have "new" version. Sorry to toss around technical details like that, but just thought it might deserve further clarification. Similarly if there is not specified memory "density" then a manufacturer might change it from older incompatible (typically too many chips) to newer compatible (typically fewer chips).
Thanks for the replies, valid points raised and the tech details may help others. I had used Crucial's website configurator, but then had my head turned by promises of extra speed with the Corsair. There may well be different modules sold with the part number, cmsx8gx3m2b1866c10. The anandtech.com entry and Amazon.com list it with a latency of 10-10-10-32 (also they list as frequently sold with a nuc). However, I bought from dabs.com (in UK), who quote a 9-9-9-24 latency; I hadn't noticed the difference previously. The retail websites universally state it is 1.35v. It's only corsair.com tech specs that say 1.5v (and 9-9-9-24).
Anyway, I'll return mine and try again.
I have the exact same issue as described but with the 16GB kit - CMSX16GX3M2B1866C10.
At least 3 of us on Amazon were able to get the NUC to post by manually loosening the timings to the 10-10-10-32 while still @ 1600mhz. A fourth customer had his ram automatically work and he had the i5 model.
I logged a support case with Corsair, but ultimately returned the ram.
EDIT: status update