Cubase not recognize connection to controller

I use a Casio Privia PX-150 keyboard (very nice by the way) as a
kb controller for Cubase 7 connected via USB.
PROBLEM:
I must first turn on the KB, and then call up Cubase in order
for the two to recognize each other. When I do it in that specific
order, I’m fine. I get sound… both in and out… life is good.
HOWEVER:
If I turn off the KB, then turn it back on again, I lose the connection.
I get nothing. Just by that simple act alone, I lose connection.
In order to restore connection, I must completely CLOSE down
Cubase, make sure the KB is ON, then re-boot Cubase again.

WHY CAN’T i SIMPLY TURN ON/OFF THE CONTROLLER
WITHOUT BEING DIS-CONNEDTED??