Visibility of Location with FOV

Orekit usage
2

According to this post the sign of the FieldOfViewDetector has to be changed

final BooleanDetector detector = BooleanDetector.andCombine(ed, BooleanDetector.notCombine(fd))

You also need to define an attitude law for the satellite e.g.,

NadirPointing nadirLaw = new NadirPointing(inertialFrame, earth);
Propagator propagator = new KeplerianPropagator(initialOrbit, mu);
propagator.setAttitudeProvider(nadirLaw);

try these changes and check if the results make more sense.