Problème Virtual Box : VT-x is not available mais est activé dans le BIOS

I don't succeed to launch a virtual os (such that Ubuntu or Debian) on Virtual Box since I always get the following error :

(VERR_NEM_MISSING_KERNEL_API).
VT-x is not available (VERR_VMX_NO_VMX).
Code d'erreur : E_FAIL (0x80004005)
Composant : ConsoleWrap
Interface : IConsole {872da645-4a9b-1727-bee2-5585105b9eed}

Nevertheless, I checked that virtualization is indeed enabled in the bios. Then, I don't have Hyper-V in my windows features but "platform of windows hypervisor" (in French: "plateforme de l'Hyperviseur Windows") and no particular options proposed. I unchecked it to try but I got more error messages since restarting my computer and trying an os on VirtualBox so I activated it again.

I don't understand the problem I have since VT-X is well in "enabled" mode in my bios.

Could you help me to find the reason I don't succeed to launch an os with VT-X not working?