Wasnt navdata api supposed to fix that.
The SU10 Navdata will surel fix the inability for GSX to obtain data from encrypted airport, but that's not the problem you are having now.
The problem you are having is that you are using a profile which has been made BEFORE GSX could read the airport data so, it used a very questionable ( and never suggested by us ) method of relying on the default airport data, which was the only thing GSX could read back then, and make a profile by moving around the gates *defined* as they were in the default airport, to match the positions to the add-on airport.
This method was very unreliable because, even if it would appear GSX would "use" the parking spots in their correct locations, they would still be named like the default airport and all the taxiway layout network would still the default one so, it might work only if the add-on airport and the default airport weren't very different, but I'm sure you would have issues like vehicles not following taxiway routes correctly.
So, the real problem is you need a profile made to work with the correct data and, as counterintuitive as it might sound, you need to use the NON-Marketplace version of the GSX profile, and if with "available online for LFBO", you mean the one at flightsim.to, I checked the file, and it comes in two versions: a Marketplace version and a Main version.
If you enable the SU10 Navdata API, you need to use the Main version, because the whole point of the Navdata API is precisely you don't need to do such tricks in GSX anymore and, assuming the Marketplace version of this scenery has the same parking spots as the non-Marketplace version, there shouldn't be any difference with the two.
I guess that profile creators that made GSX profiles this way, should rename the file or the documentation not to differentiate between Marketplace or not, but if you use the Navdata or not because, if for any reason you want to keep the Navdata option disabled, you still need to use the "Marketplace" file.