Probably you disconnected some connection accidentally. Or maybe, but less likely, you damaged something that now needs to be replaced.
The old RAM was in the same slots? So all you did was replacing 16 GB RAM by faster RAM? That should work indeed. Why slot 2 and 4, and not 1 and 3?
Are you sure the new RAM is compatible with your motherboard? From what you say it looks like it indeed.
All you can do:
1. Check all cables and connections.
2. Bring it back to the old situation (old RAM in old slots).
If it works, try again. If it doesn't work: find a repair shop.
Today I bought 2 new sticks of RAM, both are 8GB Ddr4 3200mhz Hyperx fury. I unplug the power cables, remove the old RAM, then install the two new RAM in the 2nd and 4th slots. I plug in the power cable and turned it on. After a few seconds it turns off, and repeatedly turns on and off. The monitor shows no signal at all and all the peripherals are not powering up. The GPU and CPU fans are running and the GPU's led lit up. Why is it like that? And how do I fix it?
Also, here are my specs:
Motherboard : Asrock b450m steel legend
GPU : ASUS ROG strix 1660ti
CPU : AMD Ryzen 5 2600
SSD : 480gb
HDD : 1TB
PSU : Cooler Master 650w
Old Ram : Hyperx Fury 8gb DDR4 2666mhz
New Ram : Hyperx Fury 8gb DDR4
I did not mix the 2 different RAMs together