I see, I’m no expert on these things and I use a Bluetooth dongle version myself. On mine, after I load a yr, mk and model, I need to go through a data base of pertinent PIDs and select not only ones that I want but ones that there is output for coming from the onboard computer module. If I want oil temp, for instance, and I select that but if the car’s output doesn’t provide for that parameter the gauge will 0 or no data, etc.
Unless this is some sort of ‘thing’ for this model that it doesn’t have LTFT for reason unkown that LTFT should normally be dancing around along with the STFT.
Have you tried this reader on another car?
If it also doesn’t show LTFT on other cars I’d say you have a faulty OBD reader. If it does show on another car than the OBD port on your Sentra may be at fault, bad connection, broken pin, etc. Unless, of course, it’s a thing on this model. I like to see a STFT of less than 5. More begins to be problematic but you still should be showing some value other than zero for LTFT. Hope some of this long winded reply helps.