AT Commands HM10 BLE Module - Not working
You changed the baud rate that the Bluetooth module uses to communicate with your Arduino but you forgot to change the baud rate that the Arduino uses to communicate with the Bluetooth module. These must match. From consulting the SoftwareSerial library's reference page, you can see that is set by this line of your code:



BTSerial.begin(9600)


That sets the software serial communication rate at 9600 baud. You need to change it to this:

BTSerial.begin(19200)