I bought an MSI B450M-A Pro MAX to use as a motherboard for a desktop PC.But when I installed the intended processor (purchased new) (AMD Ryzen 5 4500) and started the system, there was no display on any of the 5 display options of the Sapphire NITRO+ RX 570 / on several monitors.I then set out to fix this problem.To test the various components of the system, I purchased an AMD Ryzen 5 2400G.After installing the processor and starting the system, there was a signal on the monitor and I was able to install the operating system of my choice (Windows 10 64-bit).The packaging/box of my B450M-A Pro MAX states that this motherboard should be compatible with the Ryzen 5000 series right out of the box.To be sure, I used MSI's M-Flash function to deploy the latest version of the BIOS/UEFI onto my B450M-A Pro MAX.But even after the successful BIOS/UEFI update to version 3J0 / more specifically 7C52v3J, there was no screen output on the AMD Ryzen 5 4500.On the AMD Ryzen 5 2400G, however, there was still successful output to the monitors. (I checked this several times).This confirms that the BIOS/UEFI update has completed successfully and the BIOS/UEFI has not been corrupted/fragmented.After this, in an attempt to fix the problem, I installed/updated missing/or old drivers on my Windows 10 64-bit using the MSI Driver Utility.After the succesfull installation, there was still no output on the Ryzen 5 4500 whereas there was an output on the Ryzen 5 2400G.The external graphics card has already been tested several times and works. I have already contacted the Support of MSI, the support confirmed that my processor should be compatible with my Motherboard.
I had a similar problem with an Intel CPU and a graphics card. The only way that the box would boot was after the CMOS was cleared by a jumper on the MoBo. Consult your MoBo manual for the details on how to clear the CMOS.
Ryzen 5 Pro 4650g, ASRock B550 Phantom Gaming 4/ac, 16GB Crucial Ballistix 3600MHz, SAMSUNG 970 EVO NVMe 500GB, Super Flower Leadex III Gold 850W