With initial launch BIOS I had issues with XMP on my memory kit, updating to current version 0607 BIOS resolved issue.
Seem's strange you are having issues with 3000MHz memory.
So you are running full slots, four memory modules? If so pull all four memory modules, check serial numbers and make two kits with same serial number, confirming both kits are F4-3000C16D-16GTZR than install one kit into DIMM slots A2 and B2, confirm modules are firmly seated in DIMM slots, and restart PC into BIOS and select XMP.
Restart PC, confirm your running at 3000MHz with single kit, if so shut down and add second kit into slots A1 and B1.
Intel 14900KF ~ Asus MZ790A ~ 48GB DDR5 ~ RTX 3090 Ti ~ Crucial T700 SSD ~ SeaSonic TX-1600 ~ Praxis WetBench ~ Full Custom Water.