Help needed intermittent starting

I have changed the battery on my l322 4.4 vogue and it now refuses to start,there is now power going to the starter. I had done the reset through the instrument cluster to try and cancel the air sus inactive message to no avail . Following a drive I parked it up and couldn't restart it I checked the supply to the starter but no power checked all cables etc but nothing , I tried the reset through the cluster again and now it's starting.Is there a signal from the key to the immobiliser that could be week needing a new battery or is there a none problem in this model any help would be appreciated as I don't want to end up stranded somewhere with my young family ?