We are using the Android nRF toolbox v2.4.0 and have successfully implemented the Template app. The app will reliably connect with our device and functions well. The only problem is when we disconnect. When the Connect button is pressed and the list of "Available Devices" is shown, our device is not shown. If I restart the app, our device will always be listed. But after disconnecting and attempting to reconnect, our device is never shown. Rebooting our device has no effect on this issue. The mobile phone is a Nexus 5X with Android 7.1.1. The device is running an nRF51 with BLE 4.2 with SDK12.1. Thanks.
