I get this message at Aerosofts Olbia, LIEO, with Aerosoft A319 "This Parking is too smal for your aircraft. Ground Services are not available." The Aircraft Position seems to be ok.
If the parking spot in the scenery LOOKS correct for the airplane size, it simply means the scenery developer has set the parking radius too small, which might have been done on purpose (to exclude some AI from going there, for example) or just by mistake.
Which is why, GSX has the "Max Allowable Wingspan" option, indicated both in your screenshot AND explained in the GSX manual, which allows you to OVERRIDE what the scenery developer has set in the AFCAD as parking radius.
The small "airplane" icon will set the correct size for the airplane your are flying when you are editing the scenery.
