I should have been clearer sorry. So I had the same problem as you, but I was using the keybind for fuel and repair. When I changed it to the specific key bind for ‘add fuel’ on the ground, I didn’t have the same error.
Worth perhaps having a quick check of keybinds to see if any other options. The other option you can try is setting the fuel in the ‘manage aircraft’ section you get before accepting the flight for the final time. It gives you an option to add fuel - it DOESN"T add the fuel when you first jump in, but if you then restart the flight, it added the fuel.