I am a beginner trying to implement ble_app_uart example from SDK 15, example compiles with no problem, advertizes. LED 1 blinks when advertizing, and turns ON when connecting through PROXY application (couldn't find nRF UART in app store), when trying to connect using nRF toolbox it quits. I don't receive any data i want to send, not working with PUTTY and Termite terminals as well. I expect "uart started" message but it is empty. What might be the problem? I am using nRF52840 DK and arm keil v5.