Virtual box guest screen resolution not adjusting

On my old VB release i used to be able to grab the bottom right angle and adjust the guest screen to fill in the program window. After a fresh install +extention the resolutuin of the guest wont change. I have 3d accerelation enabled in the dispay option in VB settings. “Auto resize guest display” is unavaliable to click(it’s in grey). Any suggestions?

This bug and a workaround for it is documented here:

Kicksecure ™ in VirtualBox - Troubleshooting - Kicksecure ™ does not Start?