I am currently using a moxy unit when riding indoors, when powering up the Garmin Edge and the Trainer I receive the message that the connection to the device is not secure.
That in itself is to be expected (although I'd happily add the sensor to a list of "trusted devices" that I am aware it is not secure if that would be possible). The message despite acknowledging will often return one second after again and again. I typically have to acknowledge the message 20-30 times before I can actually use the Garmin Edge 840 unit, not sure what causes this constant repeat, but it is certainly annoying. Not sure if there is a simple workaround to switch of this message altogether or to simply ignore insecure connections coming from known devices.