Freelander 2 (LR2) keyless fob

Freelander 2 hse 2014.
Can a previously working fob loose its connectivity?
Went to use my spare fob, not unrecognised by vehicle. Had battery replaced and signal checked by Timsons.. Still not recognised
I haven't use this fob for over 6 months, it worked fine then. Does the recognition program degrade with no power over time? Presupposed the battery dead.
Is the fob board a single use?
Read some information about 12 clicks of the unlock button reestablish connection but it didn't work for me.
Thanks

I've read somewhere that a key fob that hasn't been used for a long time gets removed from the fob register in the vehicle, but I don't know how accurate this is.

I do know that my own 2009MY SE goes into low power mode if I've not used it for 28 consecutive days, but that's a different issue which effects both remote fobs.

Does the fob with a new battery open the doors? if not then open with the one that does and see if the newer one starts the car, if not then as the battery been installed properly.

The new fob does not do anything. Timsons checked the signal when they installed the new battery. I got it checked at two branches.
When I acquired the car both fobs worked ok. I had to replace the working fob battery after an advisory some time ago.