There are a few things that may cause your LEF to blink yellow.
1. Your device is attempting to connect to the last network you were paired to when you are now in a new network environment. Please make sure your device is paired to the same network as your computer. If you are having difficulty, follow the instructions here to forget the last network your device was paired to before attempting to pair in the new location.
2. Your projector is not on/in standby. Please check that your projector is still on and not in standby mode. If your device was online but your projector went into standby mode, it may blink yellow indicating it has lost connection to the network.