Sons computer stopped working ( No display). After some tightening screws , all seems to work. Except that only DIMM 1A and 1B are reported
I use 4x 2GB Gskill F3-12800CL9.

I have tested each stick and they work. If I run CPUZ it shows all slots have memory correctly.
If I am in Bios, although it only reports 4gb, However , the SPD info reads the correct memory size for each slot.

windows 10 64 bit reports 4gb, I ran benchmark and it only shows 4Ggb.

I have cleared cmos, reflashed latest bios ( ver 1903) so would appreciate some help.
thank you