When you restart TX and RX units, they won't reconnect to each other automatically sometimes. You may need to manually pairing this set.
1. Press and hold pairing button (in the middle) on both units for about 5 secs to enter pairing mode, until you see the LEDs flashes BLUE and RED alternately.
2. Wait about 2-5 seconds, until you see the LEDs on both units flashes BLUE for about 1-3 secs, also a voice prompt from the connected headphones / speaker on RX unit, indicating they are successfully connected. After that, TX unit flashes WHITE twice every 5 secs, while RX unit flashes BLUE once every 5 secs.