DN2820FYKH NUC kit - screen stays blank, LEDs signal memory issue although my memory should be compatible

Hi!

today I started setting up my brand new DN2820FYKH.

I installed a piece of 4 GB SO-DIMM low-voltage memory of type Crucial CT51264BF160BJ - which should be compatible as per Intel® NUC Kit DN2820FYKH — System memory.

Unfortunately, starting it up fails:

the LED (under the power button) immediately starts to flash three times, blanks, flashes three times again, and so on.

As per Desktop Boards — Three LED blinks when booting computer, this indicates a memory issue.

I opened the NUC (several times in fact) to make sure that the memory fits nicely in the memory slot. I'm pretty sure it does.

This type of memory should generally be compatible, as it is on Intel's compatibility list.

I'm at loss - is the NUC or memory really defective?

Or are there any other common mistakes, which I could correct myself?

Thanks a lot,

Tom