Did you leveraged the bios options of your motherboard. Did you updated your bios, APU and GPU drivers?
From what i remember there are specific options to set up to allow the dual graphics to works.
Looking your motherboard manual, here what is reported:
Step 1. Please keep the default UEFI setting of “Dual Graphics“ option on [Auto].
Step 2. Install one AMD RADEON PCI Express graphics card to PCIE1 slot.
Step 3. Connect the monitor cable to the onboard VGA port. Please be noted that
the current VGA driver / VBIOS can allow Dual Graphics output from on
-board display only. For any future update, please refer to our website for
Step 4. Boot into OS. Please remove the AMD driver if you have any VGA driver
installed in your system.
Step 5. Install the onboard VGA driver from our support CD to your system for
both the onboard VGA and the discrete graphics card.
Step 6. Restart your computer. Right-click the desktop. Click “AMD VISION
Engine Control Center” to enter AMD VISION Engine Control Center.
Step 7. You can also click “AMD VISION Engine Control Center” on your
Windows® taskbar to enter AMD VISION Engine Control Center.
Step 8. In AMD VISION Engine Control Center, please choose “Performance”.
Step 9. Click “Enable CrossFire” and click “Apply“ to save your change.
Step 10. Reboot your system. Then you can freely enjoy the benefit of Dual
If this do not work, you should maybe inquire further into the bios options, it seems there is maybe a specific set of options to set up in order to get it work properly.
You can check this video as exemple: How to setup AMD dual graphics (hybrid crossfire) - YouTube