I checked now with a 3rd party scenery with non-GSX SODE jetways ( 29 Palms EDDN ), and I can see the tanker just fine, tried with both the old default 737 from FSX, and with the PMDG 737-800, and I can see the Hydrant with both, working just fine.
Just to be clear: do you have GSX L2 activated ? The new Fuel Hydrant is the only thing in the latest update which requires GSX L2. And, it requires PBR so, it works only with P3D 4.4 and above.