Nissan LEAF 2023 Owners Manual
6.5.3.22. 30. Steering assist not available warning
This warning appears if the lane markers are not detected correctly for a certain period of time due to the conditions that wiper is operated at low speed, there is a object like lane marker in the driving lane (winter sleet, reflected light from the surrounding on a rainy day, unnecessary lane markers to be removed, etc.). If you want to use the Steering Assist System, turn off the ProPILOT Assist system, and once on a road with clear lane markers set the system again.
Owners Manual