On the Anyware Software Client for Linux using either Ctrl+Alt+SHIFT+F12 or Ctrl+Alt+F12 will switch to virtual terminal 12, which typically does not exist. This can result in a blank screen. To avoid this you can disable virtual terminal functionality by creating a file /usr/share/X11/xorg.conf.d/60-pcoip.conf with the following contents:

Section "Serverflags" 
    Option "DontVTSwitch" "yes"
EndSection

This file needs to be created with root permissions.