Qube! switched to perpetual licenses as of v6.0, but this convenience has come with a price: Qube licenses are now node-locked, and are tied to the "hostid" value in the license file, which is the MAC address of your supervisor. If your license is not installed correctly or has the wrong hostid, Qube! will show as only having 2 licenses installed.
You can check that your licenses are installed and working in the GUI or from the command-line.
The command utility "qbping" displays the license count and MAC address:
supervisor - active - tag: 10.0.1.101 D4:9A:20:0D:FB:BE 6.2-0 bld-2011.05.23.17.13.25 osx - - host - 0/25 licenses.
In the GUI, the license count shows in the title bar of the GUI, but will not update on machine other than the supervisor if you've just installed a new license.
The best way to use the GUI to check the license count and MAC is with QubeGUI->Admin->Ping Supervisor, which will display the information in a dialogue box:
If you find that you only have two licenses available, check that your license's hostid matches your supervisor's MAC address, and that the qb.lic license file is installed in the correct location
/etc/qb.lic for Linux & OS X
C:\ProgramData\Pfx\qube\qb.lic for Win7/Vista/Server2008, and C:\Windows for XP and Server2003
Also ensure that the qb.lic file is saved in plaintext format, and has not extra characters that were not part of the original license string.