Unfortunately, the HomeCortex can only be paired with the doorbell that came with the package. Adding another doorbell camera to the HomeCortex is not possible.
You would think with the money you spend everything would work together. I should have researched these are little more. The Doorbell cameras should connect to a home-base. If you bought a system with only 2 cameras the thats it just two cameras for the rest of the time you own it. You need a seperate home base for each additional camera you add. Stupid.