key fob not working

[Chris340gti]

hi all , not sure if this is the correct group but ...

so I've got this key which was used on a 2014 golf.. if worked fine until battery went , replaced said battery ... thinking it would now work fine but NO

nothing , the led lights up red but doesn't register with the car at all ..

surely it doesn't need re connecting . or does it ?? any ideas how as google says it doesn't need re connecting to car etc