Go to
Officlal > OneStore folder
Delete flybywire-aircraft-a320-neo from onestore folder or delete via content manager.

Go to
c:\Users\YourUserName\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\packages\
//steam // appdata > roaming > microsoft flight simulator > packages
Delete folder named flybywire-aircraft-a320-neo
Go to community folder
Delete folder named flybywire-aircraft-a320-neo and all liveries
Download and install latest dev version or experimental via FBW installer.
https://flybywiresim.com/
After that launch msfs and select Flybywire simulations A320neo