Hello Richard,
Thanks for writing!
This sounds like either an issue with your vehicle or your NissanConnect account.
If the official app does not work My Leaf won't either. That explains your points. I won't go into details regarding your points because of that.
I would investigate whether your vehicle has issues with its modem. Could be a faulty modem/SIM card causing your vehicle to have no network coverage. You should be able to confirm this in the infotainment system. There should be an icon indicating network coverage/connection quality.
I would begin there.
Hope you get it working!