Hi all, I had my TCU replaced on my 2015 at the beginning of last year (2019). I don't access the Connect app all that often and at the times I have - its been a bit finicky. I've even had to go to the car to log out and then log back in to "restart" the system. Recently, I was unable to use it all. I contacted the Nissan Leaf Owners Connect department customer services and because all the details of the TCU info were starred out and I was logged out of the system, I was told I would need to go to the dealer for a repair (presumably a hardware failure).
I located a YouTube video of a guy who unhooked his negative battery terminal for at least five minutes and was able to "restart" the system (TCU). I had done this procedure earlier in the day, yet did not leave the 12 volt auxiliary battery disconnected for five minutes. I tried it last night and was able to log in and see all the TCU info and the app is now functional again
I did replace the 12 volt auxiliary battery some months ago and wonder if that created/caused the issue...
Stay safe all and be well!