So my guess would be there is an issue with the fact Concorde has several fuel tanks
It's likely it doesn't just have a custom refueling system, but even extra fuel tanks in addition to those simulated by the sim, which means GSX cannot read them. Which is understandable, since the Concorde has more fuel tanks the sim can handle.
I'm afraid there's no way to fix this, other than talking with FS Labs about a way to interact with any non-standard tank they added to the simulation.
