I've checked it few min ago - it seems to batteries in all sensors are dead :-/you have the valve electronics inside the wheels, i assume, are you able to read the values with VCDS?
I've bought all new sensors but I noted today that all was produced i 11.2008.
This propably is the reason of discharge of batteries.
So, when You're buying the sensor look out not only the unused but first of all the newest/youngest.
The date should always be printed on the sensor next to part No and others marks.