Those. Problems with the Laptop and RAM, the Laptop System does not see the second bar of RAM. What to do?

Question

laptops

I've gone through so much but I just can't figure it out. So, I bought a RAM bar for a Kingston KVR21S15S8 laptop, inserted it into a laptop (ASUS VivoBook X556UQ), but it was not displayed in bios, it is visible in CPUZ, AIDA64, but not in bios, I started looking for what the problem was, got to such cases when people set the ddr3 bar where it was necessary to put ddr3l, but I have ddr4, and immediately realized that this was not my case.
Wrote in technical support on Off. ASUS website, they gave me a list of recommended RAM strips, I took and bought one of them, but what a surprise, the same problem with it (this time there was Hynix RAM with the same parameters as the previous Kingston), and here I went into a dead end.
Ps The first bar is soldered to the motherboard

Answer 1

see if the latest version of the BIOS
is, but in general with laptops especially - how lucky
the easiest way is to hand over the memory under warranty and pick up the one that will be visible in the service

Answer 2

At the expense of compatibility, look at what memory is preinstalled by the manufacturer (brand, volume, frequency) and how much your memory differs from it