Welcome!
I'm not sure where you reside. Are the steering wheel and seats warm or hot under normal conditions?
Based on what I see in the 2015 Leaf manual:
* Page 2-45, Heated Steering Wheel Switch, "If the surface temperature of the steering wheel is above 68°F (20°C) when the switch is turned on, the system will not heat the steering wheel. This is not a malfunction."
* Page 2-47 addresses the heated seats, but I don't see anything about specific temperatures. My guess is that, since the heated seat system is controlled by a thermostat, the system won't heat the seats when they are above a specific temperature.
You can obtain a copy of the manual here:
https://owners.nissanusa.com/content/techpub/ManualsAndGuides/LEAF/2015/2015-LEAF-owner-manual.pdf