The memory module you are trying to use is 1.5V and is not supported by your system.
You should replace the module for a 1.35V version (DDR3L-1600/1866 1.35V SO-DIMM)
As shown here: Intel® NUC Kit NUC6CAYS Product Specifications
You should buy a compatible memory for your NUC: System Memory for Intel® NUC Kits NUC6CAYH and NUC6CAYS . You should take care in addition to voltage 1.35V also to RAM density: Unsupported 1Gb or 2Gb Density Error for Intel® NUC Kits NUC6CAYS and... . For example Kingston memory KVR16LS11/4 appears on Intel Validated Product list and you can see it here: Kingston KVR16LS11-4 DDR3 - לנייד זכרונות חלקי מחשב or on vendor page: https://www.kingston.com/dataSheets/KVR16LS11_4.pdf
Also Transcend memory TS512MSK64W6H is validated by Intel and you can see it here: Transcend TS512MSK64W6H DDR3 - לנייד זכרונות חלקי מחשב
This message was posted on behalf of Intel Corporation
Thank you for reaching the Intel Communities.
I understand you would like to get more RAM to work with your system. We can certainly clarify that up.
In this case, the other peer is right, the required type of RAM is: DDR3L-1600/1866 1.35V SO-DIMM
As per the information found, this stick is 1.5V (http://bit.ly/2y6r9eN )
If you have further questions, feel free to contact us back.