What is your motherboard?
There is no B-450 ROG STRIX.
Is it the B450-F ROG STRIX?
ASUS ROG Strix B450-F Gaming Motherboard - Next-level performance: 2nd gen. AMD processors, 5-Way Optimization, Fan Xpert 4, Aura Sync. POWER.
rog.asus.com
If this is your board and you're on a 2018 BIOS version there are like 10+ BIOS version after the one you have.
BIOS version add memory compatibility update.
If your board is the B450-F ROG STRIX I would recommend you update your BIOS.
https://rog.asus.com/ca-en/motherboards/rog-strix/rog-strix-b450-f-gaming-model/helpdesk_bios
What is your BIOS version? Go in your BIOS and tell me the version and your motherboard model.
When you update your BIOS you have to read the BIOS description because some of them have text like this below.
"ASUS strongly recommends installing AMD chipset driver 18.50.16 or later before updating BIOS."
So you're mixing RAM? Mixing RAM might not work with the DOCP profile. RAM needs to be bought in a RAM Kit and not be mixed with different kind of RAM. It can work. It might not work. It's a guessing game when you mix RAM. I recommend you use the new RAM only by itself first.