Very often, this means that your CPU virtualization feature is disabled. Check that Intel VT-x, AMD-V and/or SVM is enabled in your computer BIOS.
If you use Windows 8/10, it is possible that Hyper-V interferes with Genymotion Desktop. Please make sure that Hyper-V is disabled when using Genymotion Desktop. For instructions on how to disable Hyper-V, please refer to Genymotion Desktop and Hyper-V (Windows 8/8.1/10)
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?