Troubleshooting Android Device Compatibility for Echo Meter Touch
If you are using a micro-USB to USB-C adapter, verify that it is a compatible adapter as described here. Also try reversing the adapter in the phone.
Verify that your phone fulfills the requirements, including OTG compatibility, list found here.
Try changing the USB configuration. This procedure gives the Android device's USB system a bit of a reset if it has gotten into a bad state and has shown pretty good success at fixing devices that are not recognizing the module at all (will not show the START button in Live Mode) and also devices that do recognize the device but only show a black spectrogram.
Close all apps.
Open the Settings app and go to System > About phone, or a similar menu, depending on your Android version
Find the "Build number" entry and tap on it repeatedly several times (you will get a countdown as you tap). You should get a notification saying that developer options have been enabled.
In the System menu, go Developer Options.
Select USB Configuration
In this menu, change the option from whatever is currently selected to a different option, other than "Charging", we recommend trying "Media Transfer", "RNDIS" or "MIDID". The actual choice is not so important as the device will reset to what is needed for any attached device. Just the nature of changing this setting, resets the USB system.
Restart the phone.
Open the EMT app and plug the module in.
If nothing improves with the above procedure at, try changing the USB Configuration and then restarting the phone a couple more times. We have see cases where a phone started working perfectly after repeating these steps a few times.