First do you have your Monitor cable connected directly to your Motherboard's Video Output ports and not your GPU card if you have one installed?
The IGPU delivers video output to your motherboard's video ports and not your GPU Card if you still have one installed.
If you do have it connected to your Motherboard's Video port then go to BIOS and make sure you have the BIOS setting for IGPU and GPU set to "Auto". If it is set for just the GPU card it will disable your IGPU. In "Auto" it will make your GPU card automatically the Main Display Adapter and your IGPU secondary Adapter.
When you upgraded your CPU did you check to see if the RAM you have installed is compatible with the new processor?
I see that it doesn't have a RX-5X00G QVL LIST for RAM but a RX-3X00G list. So I would use the RX-3X00G List to at least see if your RAM is compatible with your 3000 Series APUs.
I would install just one stick of RAM then do a Clear CMOS to reset your BIOS back to its default settings and see if it boots up.
If not, as mentioned by the other User, post what Motherboard Trouble LEDs or Digital Code is showing to see which hardware is not passing the POST Test of BIOS.
NOTE: By blank Monitor you mean no video output correct?
When you boot up wait a few minutes and see if your get video output once Windows starts loading unless the boot process is stopped at a specific Trouble LED light or Digital code and the booting process is halted.
