if the car was a second hand one it could have had extra keys paired to it and filled up all of the memory locations for keys, or you could have filled them up with 3 or 4 failed attempts with one key
if you get a
problem like yours you need to delete all keys in the memory and start again
this will be a dealer job or you can do it yourself if you have the vag-com software and a lead to plug into the car
if you go to a dealer don't forget to give them your spare key too