In Aerosoft EBBR, GSX is always sending Fuel Truck instead of a Hydrant that results in rapid fueling with PMDG 737/738. I have verified the height of the fueling point that is more than 3.4m.
The only possible explanation, is the height is not higher than 3.40 from ground, which is what normally is if you use the configuration that comes with GSX, that places the refueling point in its realistic location, which IS lower than 3.40 from ground.
If you edited the airplane to move it outside, to force the platformed vehicles to arrive, so you are sure the height is higher than 3.40 from ground, even taking into account the airplane weight that might put it below that, even if so slightly, than you need to clarify what do you mean with "4 parkings and all of them have underwound fuel reservoir".
Do you mean you see a ground texture that comes with the scenery ? If yes, that wouldn't be enough to consider the parking to have underground refueling, since the airport textures that comes with the scenery cannot be read or understood by GSX, and there's no data in the parking specifications that will tell that.
By default, lacking any airport customization made in GSX, what makes GSX decide if a parking spot should have underground refueling or not, is the presence of a Jetway. Of course, this is just the default so, with customization you can either disable underground refueling when there's a jetway, or enable it when there isn't one.
So, assuming you are absolutely sure you edited the airplane to have the refueling point high enough with a platformed vehicle, what you are supposed to see is:
- An Hydrant, with a crew of 2, on gates that have jetways, provided the "underground refueling" property in GSX customization haven't been edited to manually disable it.
- A Fuel Tanker, with a raised platform with 1 guy on it, on parking spots in the open OR gates where the the underground refueling has been explicitly disabled.
That because both vehicles require a refueling point > 3.40.
If you are seeing something else, like a Fuel Truck with no raised platform and no crew, then it can only be because the refueling point of the airplane is < 3.40, no questions about it.