I have a 2011 A4 Premium Plus with 79.000 mile on it. The other day my key fob stopped operating the door locks and trunk release. It does start he car. The first thing I thought of was changing the battery in the fob. I have owned it since 2013 and it has never been changed. I replaced the battery plus the battery in the spare fob but nothing has changed. Neither will operate anything but will start the car. Any idea of what the problem may be here?