I had same problem with z370-h, i5-8600k,
Crucial 16GB (2 x 8GB) Ballistix Sport LT Gray
DDR4 3000
Installed as motherboard manual, slots A2, B2 did not boot, only dram light goes on. Got them working with slots B1, B2, but not dual channel.
I removed cpu and cooler, didn't see anything wrong...