Hello,
Check the manual again as you actually did have the sticks in the right slots.
You must use either the Grey slots or the black slots.
It goes something like this,
Channel A = DDR4_2 + DDR4_4
Channel B = DDR4_1 + DDR4_3
However, look at how it is ordered in the manual, its not 4,3,2,1.
DDR4_4.....DDR4_2.....DDR4_3.....DDR4_1
It is 4,2,3,1
Make sense?
Essentially you need to use same colour slots.
As to your problem, you need to determine if both memory modules work individually and if both memory channels work independently.
Make a note of your memory sticks / keep track of which one is being used (I'll refer to them and stick A and Stick B)
Place only Stick A in Grey DIMM slot closest to the CPU.
1) Does the PC boot?
Place only Stick A in Grey DIMM slot nearest right side of the board.
2) Does the PC boot?
Place only Stick B in Grey DIMM slot closest to the CPU.
3) Does the PC boot?
Place only Stick B in Grey DIMM slot nearest right side of the board.
4) Does the PC boot?
This will help determine if channel A or Channel B is dead and if Stick A or B is Dead.
BTW, what is the part number for your Kingston kit?
Before you do this clear the CMOS and remove everything that is not required to boot the PC.
E.g GFX card and use the integrated GPU.