Hi Pete , when you release the access section on the back to get to batteries " looks like size £1 coin with slit on it " when it comes out there is a rubber ring on the male side , check that this hasn't jumped off , also make sure you have put batteries in right way up , then the metal strip should be attached with a slight "spring " so it connects properly I>E> giving positive feed for connection of fob . then finaly when you have checked all that , on the actual fob where the hole access is for batteries if you look on the fob where the access hole is. at the top of the rim of female hole there is 2 tiny triangles one on left about 11.00 oclock and one on right about 1.00 oclock, so when you put back the male bit into the female section you will see the raised line on the £1 male section so twist and gently press with screwdriver at same time so that the raised line turns to the right side at 1.00 oclock . job done fob should work perfect . sorry its a bit longwinded , but believe me that little rubber ring over the years has cost owners thousands of pounds and I have witnessed cars being scrapped over this as they lost all accessibility ,,, new key-fob from main stealer "suggest key 4 … " cost approx. £147.00 ordered by stealers to huff in germany . 3 days delivery to your dealer , just plug n play no dianogstics required or syncing etc it self syncs automatically .. cheers Mozz……. if u have problem ring me