HELP! Key fob triggers alarm

[Silasc]

HELP. Have a 2008 525i saloon. Am having issues with the key fob. After 5 weeks of not using the car, on inserting the key into ignition, the alarm is triggered. I can still start the car with start/stop, but alarm continues, only stopping when key is taken out of ignition. Battery/key icon on dash appears. AGM BMW main battery is showing 12.4 volt charge – is it a simple case of battery top up?. I disabled the hood sensor, just in case that is at fault. The fob is the sealed unit – can't replace battery. Any help welcomed.