Genymotion Desktop 3.1 is not compatible with VirtualBox 6.1 yet. If you are using this version, please downgrade to VirtualBox 6.0.4.
You can find it here: https://www.virtualbox.org/wiki/Download_Old_Builds_6_0.
If you are using a VPN, stop your VPN or refer to the article Genymotion Desktop and VPN.
Make sure that Intel VT-X or AMD-V virtualization feature is enabled in your BIOS. Please refer to "Your CPU is incompatible with virtualization technologies" error for more details.
Make sure that Hyper-V is disabled when using Genymotion Desktop. To easily disable and re-enable Hyper-V, please refer to this article Genymotion Desktop and Hyper-V (Windows 8/8.1/10)
The Memory Integrity Core Isolation feature of Windows Defender is known to cause this type of errors. Make sure it is disabled before using Genymotion Desktop. For more information, please refer to How to disable Memory integrity in Windows 10?
There may be a problem with VirtualBox Host-only interfaces. For more details and other solutions, please refer to "Unable to start the virtual device" (Windows 10)
If none of the above worked for you, try to re-install VirtualBox and Genymotion (See How to uninstall Genymotion Desktop completely (purge)?)