The MSFS Weather Radar API does not allow for a true representation of the Weather Radar on the real Airbus A320. With this in mind, you may sometimes experience rendering artifacts or a lack of any radar return in situations you would otherwise expect it. This is out of our control for now until future improvements to the MSFS WXR API.
If you have no returns at all, it is possible you have "USE DISPLAY SAFE MODE" checked in the Fenixsim A320 App. This rendering mode is not compatible with the MSFS WXR layer. You should uncheck this option to utilise the Weather Radar.
You may also experience incorrect radar returns if the MSFS Graphics Option "Glass Cockpit Refresh Rate" is set to anything other than "HIGH".