PC doesn't boot after RAM replacement

I bought two used sticks of AMD Radeon™ R5 Entertainment Series 4GB (1x4GB) DDR3-1600 MHz CL11 R534G1601U1-G ram to insert into my Asrock P55DE3 motherboard, but no matter what I tried the system doesn't start - no bios loaded, no beeps, just black screen and motherboard keeps restarting after some seconds. I read manual.pdf but there is nothing special, except for advice to try B1 slot first of all, I also read QVL.pdf file and AMD ram is not listed there (though I don't expect every single ram to be listed). The ram sticks are of proper frequency and seem to be supported. I don't exceed 16GB motherboard RAM limit. My old working sticks are Kingmax 1GB, Kingston 2GB, Hynix 4GB, all of 1333Mhz frequency, working separately and all together.

I tried:

• Resetting CMOS by jumper
• Single or both sticks (in proper dual-chael slots) inserted
• Setting lower frequency (1333 Mhz, 800 Mhz) in BIOS while my old RAM inserted, replacing stick with the new ones after that
• Setting Overclocking mode in BIOS with 1600 Mhz explicitly, using my old RAM, then switching the RAM to a new one.
• Setting higher DRAM voltage up to 1.9v, though it should work with 1.5 v (I'm pretty noob in hardware, so I did what I could think of. I was afraid to increase voltage more, though possible)
• Begging "Please work"

Right now I don't have a possibility to check the RAM at someones other PC, so it might be faulty. Though I hope it's not. As a side note, I recently tried 8GB new stick (which is evidently not supported) and the symptoms were the same, so it makes me think there might be something else wrong.

Could you please suggest what else I may try to make it work?