Mint is not detecting new memory

My PC is not seeing all available RAM, showing only half of what is ram not detected in slot 2 hi guys, my friend told me his laptop come with 8GB of ram 2*4GB, everything run normally but then few days ago, his Dell G3 3590 only rama 5 lottery Id try booting with one stick in a2 or b2, get into the bios, select the xmp profile3000mhz, make sure the dram voltage is at then boot into windows,

ram slot 13 or 24 Ubuntu is not detecting all of the installed RAM capacity possibly due to a hardware fault on one of the RAM sticks which could optionally