@Fardeen Chy I am no expert but I will try to help. The slot to put the memory is the second slot closest to the CPU. Memory goes in 2/4 not 1/3 for Dual channel (motherboards with 4 memory slots).
Please make sure the memory is in that slot.
If you still need to do a BIOS upgrade you can possible do that via a USB drive. On my MSI B450 motherboard I an plug in a USB drive with the bios upgrade (specifc slot on the motherboard and it will updated from there). Sorry, but I do not know if the Tachii will support this. Your motherboard manual should specify if this is possible.