I also find that the wipers take time to recognize new rain, so I just do a manual quick-swipe (mist) and that seems to trigger the auto-system and it works fine from there. Just FYI.
I would doubt it is the radio hardware if other audio functions work. Are you sure that the nav voice is turned up? Check this by entering a route and having it speak the direction and then turn up the radio volume WHILE the direction voice is active.
The same model works on my '23 CX-50 (only the addon adapter harness is different) so I'm pretty sure it will work on the newer CX-5 too. Just be sure to get the correct plug/play adapter harness.