eLicenser for Studio 4 not license for essential 4

Ok is this correct?

I can home from work today and plugged in my USB eLicenser key to setup some projects for a class tomorrow that will be using cubase essential 4. I must have picked up the wrong USB key as this key is a Cubase Studio 4 key and not the lower essential 4.

Now i thought that this key should hold all the lower version licences but it will not allow me to run Cubase Essential 4.