H370 Pro 4 - Black Screen. Memory?

Hello ASRock Forum,

thanks agin a lot for helping me out with my question regarding the M.2 drive.

I assembled the parts today very carefully, but however, the GPU output is not working. The CPU (boxed cooler) and the housing fans run, but I do not get a display signal and so I am not able to access the BIOS. The PC did not send any accoustic signal.
I checked it using the VGA-Port and also HDMI. There is no dedicated GPU installed, I wanted to use the onboard GPU, as I also do on my old ASRock driven PC.
Probably, I chose the wrong memory which I installed in slots A1 and B1. Probably DDR4-3200 is to far off from the normal specs. I thought, they would be backward compatible.

My setup:
- ASRock H370 Pro4 Intel H370 So.1151 Dual Channel DDR4 ATX
- Intel Core i5 8600 6x 3.10GHz So. 1151 BOX
- 32GB (2x 16384MB) G.Skill RipJaws V black DDR4-3200 DIMM CL16-18-18-38 Dual Kit
- 500GB Samsung 970 Evo M.2 2280 NVMe PCIe 3.0 x4 32Gb/s 3D-NAND TLC (MZ-V7E500BW)
- 2000GB WD Blue WD20EZRZ 5.400U/min 64MB 3.5" (8.9cm) SATA 6Gb/s (not yet installed)
- 450 Watt be quiet! Straight Power 11 Modular 80+ Gold
- be quiet! Pure Base 600 Midi Tower


Photo attached. Cable management will be done later.

Any hints would be highly appreciated. Thanks in advance!