Difficulty in Loading fuel into the A320neo (LEAP)

I have difficulty in adjusting/increasing the fuel in my FlyByWire A320neo. Each attempt wnds up returning to the default fuel quantity which is so small it can’t take me on a long flight. I have tried this at the airport fuel points but to no avail. Please can anyone help me out?

If it’s the FBW add-on you are using, you must manage fuel in the EFB. You can’t use the sim load and weight menus.