SL3 rewire to Reason 5

I’m new to all this, but I’ve successfully installed Reason 5 and Cubase SL3.1.1 on a Mac OS X 10.6.8 machine.
Both softwares run fine on their own.
But I can’t get Cubase to see reason as a rewire option.

When I try and open Cubase first and then Reason, it gives me an error “Cannot open the Reason Engine”

Can anyone help?
I’m nervous that these two pieces of software are not compatible.