Will be really helpful to know your computer information and Windows version installed.
If Windows 10, go to Task Manager and see if it shows 1 Core with 2 logical cores. It should show correctly 2 cores with 4 logical cores.
If it doesn't, try going to Administration Tools - System Configuration - Boot - Advanced Options - Number of Processors: input 4 cores and restart your computer and see if it shows all 4 "Logical" cores in Windows Task Manager.
Also check in BIOS/UEFI that you don't have any cores disabled.
If you already checked that why didn't you mentioned it in your original post?
As far as I know, most Users can't read your mind.
Please show in Task Manager the CPU and not the Memory. In the CPU it will show how many Cores are active or showing.
The first thing you must do is update your Windows 10 Pro which is the original version 10240 (Also not Supported by MS with Windows Updates anymore) you have installed to the latest version Windows 2004. Once you do that your APU should show the correct amount of Cores active.
Also update your ASRock BIOS and CHIPSET and Graphics once your update Windows 10 Pro to version 2004 from ASRock Support download page for your motherboard.
Once you update Windows to the latest version see if it show 2 Cores with 4 Logical cores in Task Manager. If not please post back with any errors or problems you have while updating or after.
Reset CMOS and repeat the Windows 10 setup with a USB stick. There is nothing different you can try.