I used both CHIRP and a software called ZT-V68 to make sure they are identically programmed. So both in CHIRP and in ZT-V68, when I download the settings from radio one and then compare them to the downloaded settings from radio two (making sure that it is actually downloading and showing me the new data from the other radio) — these software data files look identical. All the settings are the same. I disabled the "scrambler" in everywhere, and set all channels to "low".
But the radios are not communicating with each other. Why on earth can that be?