My old Marlin configuration.h file has this little gem hidden inside it:
// Deltas never have min endstops
#define DISABLE_MIN_ENDSTOPS
Since M119 isn't showing the MIN endstops, I'm guessing that yours has the same setting not commented out. Put a double slash in front of it (to comment it out) and see if M119 shows all six endstops.....
// Deltas never have min endstops
#define DISABLE_MIN_ENDSTOPS
Since M119 isn't showing the MIN endstops, I'm guessing that yours has the same setting not commented out. Put a double slash in front of it (to comment it out) and see if M119 shows all six endstops.....