Ho fatto la prova varie volte, ho provato anche a usare gli altri due slot, riprovo un altra volta
ho trovato questo online
I had the same problems as described above, if I used slot A.2 and B.2 the PC didn't boot. It worked in B.1 & B.2 but obviously without Dual Channel.
I changed the XMP profile from auto to the other profile that was listed
I disabled the ASRock DRAM Frequency Optimization (all the way at the bottom in DRAM Timing Configuration)
Now it boots with the RAM in A.2 and B.2 in Dual Channel
ASRock Z790 Steel Legend WiFi (UEFI Version: Z790 Steel Legend WiFi 6.02)
Corsair Vengeance CMK32GX5M2B5600C36 2x16GB
FUNZIONA