There can be two reasons:
1) the clicker might have lost the voting channel.
The old type of clickers have a button "Go" while the new clickers have a button "Chanel". If a student presses one of these buttons the channel will be changed and the clicker will lose the connection with the receiver and will not send the votes. Standard Channel 41 is used.
To reconnect press combination "Go 41 Go" or "Channel 41 Channel".
2) the battery might be empty. Please return the clicker separately to be fixed.