Every time I've had a software update fail to install it's been down to low charge on the 12v. A trickle charge solved the problem every single time. These vehicles absolutely benefit from regular driving and if you aren't using it enough occasional trickle charging. I have the CTEK that the OEM Land Rover charger is based on.

 

CTEK seems to be popular for European cars. I have used both Battery Tender and NOCO with good success. Make sure it is set for AGM. Higher the Amp quicker the charge, but time should not be an issue.