Windows server 2008 r2 sp1 x64 or BIOS does not see all installed RAM, what should I do?

Question

RAM

Build:
windows server 2008
Asus B150M-A/M.2
Intel Core i3 7100
Previously, there were two bars of 4GB kingston ddr4. Now we've decided to increase it.
Bought two more 4gb Kingston sticks.
In the CPU-Z program and in the BIOS, he sees all 4 bars. Total should be 16GB
But windows sv-wah writes 8GB (available 7, 88)
Why and how to fix it?)

Answer 1

Have you tried updating the BIOS?