Good morning
I used the latest release of the host computer with Windows 7 64-bit, and virtualized Windows 10 after installing the Guest Additions, I can not get the whole screen.
I tried several times by restarting the virtual machine, no way I can not get the whole screen.
I uninstalled and reinstalled Virtualbox the previous version (5.0.14-105127) and its Guest Additions, the full screen feature now works perfectly
Thank you