what happens if you call the full path of the GPT?
e.g./usr/local/snap/bin/gpt -NdviOp -h
INFO: org.esa.snap.python.gpf.PyOperatorSpi: Python operator ‘py_sambuca_snap_op’ registered (Python module: ‘sambuca_snap_op’, class: ‘sambuca_snap_op’, root: ‘/Users/MYNAME/.snap/system/modules/org-esa-sen2coral-sen2coral-inversion.jar’)
INFO: org.esa.snap.python.gpf.PyOperatorSpi: Python operator ‘S2RutOp’ registered (Python module: ‘s2_rut’, class: ‘S2RutOp’, root: ‘/Applications/snap/s2tbx/modules/org-esa-snap-snap-rut.jar’)
INFO: org.esa.snap.core.gpf.operators.tooladapter.ToolAdapterIO: Initializing external tool adapters
INFO: org.esa.s2tbx.dataio.gdal.activator.GDALDistributionInstaller: No distribution folder found on Macintosh.