I have created the Default MonkeyC Project through VSCode, set the minimum supported API to "3.0.0 - System 3", selected "Edge Explore" as the target device, and built the PRG file. Then I have side-loaded the PRG file to a USB-connected Edge Explorer running Software Version 5.4.0. The app is in the "Apps" folder (Garmin -> Garmin -> Apps) but when I tap the IQ button I get the message "No Connect IQ apps available".
Cycling the power does not change the result. There are no logs. After unplugging the device from the USB cable and plugging it back in, the PRG file is still in the "Apps" folder. But the app never appears in the ConnectIQ apps list.