Ram your using on Phantom Gaming 4 board?

New member here but have been using Asrock MBs for the last 10 years.
A little late on a reply but just got this MB last week. I am running this board with an AMD Ryzen 5 3600 CPU and 32GB ram - 2 kits of CORSAIR Vengeance LPX 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800). After all these years, I should no better, I did not check the memory compatibility list for this MB. I saw the sale price on this ram on Slickdeals, $60., free shipping for a 2x8 GB kit and ordered 2.
Like the OP at first with 2 sticks of ram I could not get this MB to accept the XMP profile. It kept the ram at 2133 Mhz. Correct me if I'm wrong, I used slots A2 and B2. I tried flashing it to bios V1.10 but then it would not boot, had to clear the CMOS and flash back to 1.00.
I did a Google search and found that others were also having the same problem with Asrock AMD MBs.
I next placed 2 sticks in slots A1 and A2 and the MB took the XMP profile. I added 2 more sticks to slots B1 and B2 and the ram was still at 3600 Mhz. Booted into Windows. According to CPU-Z the ram was still at 3600 Mhz.
Then the multiple BSODs started appearing, several different error messages.

I checked each chip in slot A2 at 3600 Mhz with the latest version of Memtest86, 4 passes, no errors. Then in pairs (kit) at 3600 Mhz, no errors. Then all 4 at 3600 Mhz, no errors, but still kept getting different error message BSODs in Windows.
I set the ram to 3533 Mhz and checked it with Memtest86, no errors. So far no BSODs. If I start to get BSODs I will probably set the ram down to 3200 Mhz.

If you plan on getting an Asrock B550 MB I would pick out one of the 3200 Mhz rams from the compatibility list.

Raining here all weekend so thought I'd mess with the ram again. This time I used AMD Ryzen Master. In Game Mode set it to Auto Overclocking and the memory clock and fabric clock to 1800. Checked it with CPU-Z and the ram was at 1800 in the bios but the timings were higher than the XMP profile, 26-25-25-25-58-85. It booted into Windows. Reset the timings back to XMP profile's 18-22-22-22-42-65. It went into a boot loop. Voltage was still at 1.35V. Managed to get back into the bios and tried increasing the ram voltage to 1.40V, No go. Set it back to 1600. Stuck there for now.

Flashed bios to V1.4. Still can not set ram XMP to 3600. Stuck at 3200.

Sup guys, I had this issue as well. I had 2x 16gb 3600mhz Vengeance RGB sticks where it detected at 2133mhz and I was able to bump it up to max 3133mhz. I have found a fix for me after 1 whole day of trying any of my solutions from overclocking and much more tinkering. (it's now 3600mhz)

The fix is quite simple.

1. I had my 2x DRAM sticks in DRAM slots A1 & B1
2. Relocate the 2x DRAM sticks into slots A2 & B2 as it has more support for faster sticks in the B550 Phantom Gaming 4 Mobo unlike A1 & B1.
3. Get into Bios and put on the XMP profile & bump it up to the speed it's manufactured for (3600mhz for mine)

*If you get 2 red lights on your GPU & DRAM mobo leds after putting it in the new slots, it just means you haven't actually pushed the DRAM all the way in. I pushed it a little more and heard new clicks and it got fixed.