Installation failed with message null

I have a problem with android studio and genymotion. I have a AMD processor that doesn't not support vt-x that is why i use genymotion. When I try to launch my simple app I get this error:

Installation failed with message null. It is possible that this issue is resolved by uninstalling an existing version of the apk if it is present, and then re-installing. WARNING: Uninstalling will remove the application data! Do you want to uninstall the existing application?

I have: Windows 7 Android Studio 2.1.2 VirtualBox 5.0.20

Please need some help !