Probably then that you're using pins 0 and 1 for the BT, which the Arduino needs to upload.
Leave the BT off until it's uploaded, or move the BT to two other pins and use SoftwareSerial.
Probably then that you're using pins 0 and 1 for the BT, which the Arduino needs to upload.
Leave the BT off until it's uploaded, or move the BT to two other pins and use SoftwareSerial.