Consider this scenario:

1. You have hyper-v installed on a windows server/client OS and it’s working fine
2. You install oracle virtual box or any 3rd party virtualization application on machine and it fails with below error:

VT-x/AMD-V hardware acceleration is not available on your system. Certain guests 
(e.g. OS/2 and QNX) require this feature and will fail to boot without it.

Or vice-versa.

Turns out this behavior is by design. Many virtualization applications depend on hardware virtualization extensions that are available on most modern processors. This includes Intel VT-x and AMD-V. Only one software component can use this hardware at a time. The hardware cannot be shared between virtualization applications. Resolution steps for it are covered in the article link. Basically, it is to disable/remove hyper-v role.