nRF52 DK won't connect with Android phone unless serial monitor is open.

[Phreaknes]

I'm just getting started with the NRF52DK, Mbed and BLE development. I started with the BLE LED demo(https://github.com/ARMmbed/mbed-os-example-ble/tree/master/BLE_LED) that I saw at a trade show. I compiled in mBed and copied the .HEX file to the DK and opened the nRF Connect app. I can see LED in the scan and when the text is black I try to connect but it fails.

If I open Docklight, set it to serial monitor to the COM port and start monitoring, the nRF Connect app and the demo works. I can turn on and off the LED by sending 01 or 00. Turn off the Docklight, Can't connect. 

Any ideas?

[Kenneth]

Hi, there is currently no ongoing development work with mbed, instead I suggest to check out zephyr-OS or nRF5 SDK. That said, it may that other developers here that may be of assistent using mbed or possible you can check out forums on mbed.org for help.