show us your settings. this could be any number of things.
For example, if you go to a location that has no nearby pokestops, it will go IDLE.
If you dont have the right settings, such as loot or catch stuff, it will go IDLE.
If you zoomed out of the map and scrolled to the left or right to find a location, you may have glitched the map and be at gps coordinates that dont have anything.