Just an update if anyone else might be helped. There is a way to open the rear fuel cap without opening the doors with some tools you can carefully bend the flap slid accross a flap and expose the lock mechanism that is attached with a hex bolt. I did not think that the keyfob had lost its access to...

So a battery place checked the aux battery and main battery and swapped the battery from the key fob still no game.

Is there any way to "re-pair" the fob to the car?

So after a nice 3 weeks holidays the Volvo Battery on my -18 S90 was completely flat, been trying to kick it back to life for a few days and seems to be ok ish, only thing that developed now is that the car can't be locked or opened with the fob. thought I'd look at that issue bit further down the l...