DAB antenna's' - one is in the roof pod, the other is in the rear spoiler, it also has the FM antenna and an amplifier / splitter attached. The first thing to do is check for any DTC's, this will 'prove' connectivity to the amplifier(s) but not beyond, then you need to lift - not remove, the rear spoiler to check the antenna on the right is connected to the amplifier, whilst you're there, check the ground plane under the amplifier for corrosion on it's mounting bolt which is one of the hinge studs. Also check both hinges have the ground strap fitted and not corroded under the fixings.
Common issues are amplifier/splitter on the RH of the tailgate, either defective or a poor ground plane connection (it's actually a ground plane for the antenna, not the amplifier but incorporated into the amplifier assembly), water ingress into the roof pod - this will only affect DAB as it's an L band antenna, other than that, occasionally there are issues with the receiver overheating but this will manifest itself as reboots not missing signals. It's unlikely to be damaged antenna cables as that would set DTC's and you wouldn't really get any FM reception at all.
