Latitude 5400 upgraded memory not detected

Hi all,

I bought a kit on rebate of 2 x 16GB Kingston HyperX HX426S15IB2K2/32 to replace the 1x8GB Hynix HMA81GS6JJR8N-VK and the laptop doesn't detect it.  I tried every combinations mixing these memory modules without success.

https://www.kingston.com/datasheets/HX426S15IB2K2_32.pdf 

https://memory.net/product/hma81gs6jjr8n-vk-sk-hynix-1x-8gb-ddr4-2666-sodimm-pc4-21300v-s-single-rank-x8-module/  

Comparing Hynix spec sheet with Kingston spec it differ mainly on the timing CL 19 versus CL 15. (same SODIMM 260 pins, DDR4-2666MHz, PC4-21300)

Should I return the HyperX and look only for CL 19  memory?

or should I reset the RTC?

Thanks