Connection is a two stage process:
1 – app connects to the Bluetooth module
2 – the app connects to the dropController sketch.
If you are connecting to the BT module this I suspect the issue is with the connection between the Arduino and the BT module. Double check the connections; RX is pin 14 and TX is pin 15.
#include
SoftwareSerial BTserial(14, 15); // RX, TX
I remember having this listed incorrectly in the past.