yeah give it a wack to work - for me it was the left side of the fob off a wall!! but as pointed out there is an issue with these - the battery has tags that go through a PCB and get soldered in. One of these tags has been cut too short and therefore did not get enough solder.
I was put off fixing mine as i seen the mess that some people made opening them. i got mine open by squeezing it in a vice, length ways each corner and side - just enough to distort the plastic and break the seal. I got the battery soldered up with plenty of good old 60/40 - tin/lead this fancy lead free stuff aint as good- still not approved for medical products, and glued back up with loctite 460, good as new!!!
couple of other points to mote,
the battery will only charge while driving and with the buttons face up.
also my old fob was worn -buttons must have got swollen as it was getting caught in the dock.