To summarize what the other posters have said, there are two things at play here.
1. The CM15A will only pass RF commands onto the powerline for those housecodes that you tell it to. That setting is in the "Hardware Configuration" window.
2. The RF receiver on the CM15A has a much shorter range (in most cases) than the TM751. There are a number of fixes for this, ranging from the very simple (relocate it to a place where it is closer to the RF signals it is trying to receive), to the mostly simple (tape a 19-inch length of wire alongside the CM15A's external antenna - no electrical connection involved - to act as a passive reflector), to the more advanced (open up your CM15A - voiding the warranty - solder in a connector, and build your own external antenna to the proper specs).
Personally, I've done the second one (the non-invasive passive reflector), and I now have good RF coverage in my entire home.
You should be able to test problem #1, by trying to use the KR22A a few inches away from the CM15A (without the TM751 plugged in). Once you have that working, you can determine the range it had by slowly moving away, until it no longer triggers.
At that point, one if the antenna mods is probably your best bet to increase the range.