Something wrong with my Bluetooth communcation

I am trying to use JY-MCU to make Bluetooth communication with my PC and Arduino DUE. At first Arduino can receive commands from PC, but recently it cannot work. I tried to change TX&RX ports or use Android phone as master device, it just received nothing. But the Bluetooths can still match each other.
I wonder the slave Bluetooth is broken as I removed the shrink. But I’m not sure about this. How can I find out the reason of this problem? Thank you in advance.

I have bought a new slave Bluetooth, it showed the same result as before. Now I can make sure that it is not the problem of Bluetooth (master and slave), ttl uart and the Arduino board. If I just connect the RX and TX of TTL to Arduino, it can receive what I send, so the code works.

I am very confused what wrong it is , can someone help me? Thanks a lot!

bttest78.ino (629 Bytes)