This error usually happens in the following situations:
You are running Genymotion Desktop in a virtual machine
Genymotion Desktop has been designed to run in a physical environment, not in a virtual machine. For this reason, nested virtualization is not supported and Genymotion Desktop will not work if run in a Windows, Linux or macOS VM.
For more details, please refer to Can Genymotion Desktop run in a virtual machine?
Your CPU does not meet Genymotion hardware requirements
Genymotion needs hardware virtualization to run. While almost any recent CPU support this feature, some old and low-end CPUs don't.
Make sure that your CPU support virtualization. See What are Genymotion Desktop requirements?
Virtualization (VT) is disabled on your host machine
All modern CPUs support virtualization (VT), but this feature is often disabled by default.
Check that Intel VT-x, AMD-V and/or SVM is enabled in your computer BIOS - please refer to your computer manufacturer user guide to find how to access the BIOS.
If you are using a computer with Windows pre-installed, you may not be able to access the BIOS at start-up. In this case, just follow the instructions from these articles:
Hyper-V (Windows Professional/Enterprise)
If you use Windows 8-10 Pro/Enterprise editions, it is possible that Hyper-V interferes with Genymotion Desktop. Please make sure that Hyper-V is disabled when using Genymotion Desktop. For detailed, please refer to Genymotion Desktop and Hyper-V (Windows Pro/Entreprise)
Memory Integrity Core Isolation (Windows)
If you have Windows 10 update 1903 (Windows 10 May 2019 Update) or above, the Memory Integrity Core Isolation feature of Windows Defender is known to cause this error too. Make sure it is disabled before using Genymotion Desktop. For instructions, please refer to How to disable Memory integrity in Windows 10?