hi mate ,my neighbour had an A4 saloon next time i bump into him i'l ask him if he know's how to reset the key remote sorry i can't be more of a help is there any info in your owners manual for your specific model
I've just looked in my owners handbook and to resynchronise the remote key press one of the buttons on the remote control key insert the key into the door lock and either lock or unlock the vehicle once [the resynchronisation process should not take more than 1 minute]
I had an l plate 100 avant and you had to reprogram the key. i can't remember how but vaguely remember having to put the key in the lock an locking the car and holding the key in the lock position for a period of seconds. i think i had to use the nearside lock hope this helps
just to say hello the name is rob as you may have guessed. I did have an L plate 100 avant about 8 years ago then sold it but now im back. bought an A4 convertible yesterday pick it up next week some may say im having a mid life crisis but i dont care am nearly fifty ha ha let the good times roll.will post pics when its clean if i can get my sons to do it.