ASRock Z790 PG Sonic Memory Issue

Hi, i bought the ASRock Z790 PG Sonic at 2024-05-18 and stumble into the same issue. I have bought a 64 GB Kit consisting of 2x32GB from Corsair. It is Corsair DIMM 64 GB DDR5-4800 (2x 32 GB) Dual-Kit (CMK64GX5M2A4800C40). In the recommended combination A2-B2 it does not work. The A1 and A2 slot do not work in any combination.

I tried every combination.

A1     A2     B1     B2     works?     combi
X     o     o     o     No     A1
o     X     o     o     No     A2
o     o     X     o     No     B1
o     o     o     X     Yes     B2
X     X     o     o     No     A1-A2
X     o     X     o     No     A1-B1
X     o     o     X     No     A1-B2
o     X     X     o     No     A2-B1
o     X     o     X     No     A2-B2
o     o     X     X     Yes     B1-B2

The modules are sold as DDR5-4800. In the BIOS they show up with 3600.
It is difficult to determine are Corsair not supported or the mainboard or the ram are defect.
At this link https://pg.asrock.com/mb/Intel/Z790%20PG%20Sonic/Specification.asp#MemoryRPL the Corsair modules are not mentioned. May this is the cause?

JCLentine wrote: Two-ish months later. ASRock replaced the motherboard, Intel replaced the CPU and Corsair replaced the memory with a matching kit. The only change is that 2 memory sticks work in the B_1 and B_2 slot. The manual says it should be B_2 and A_2, yet that configuration does not work. It's very hard to judge if I'm doing something wrong, there is no documentation about the BIOS (or UEFI) This is ridiculous.