So your atmosphere trigger should look something like this (click spoiler to expand images):
Lightprobe placed inside of the atmosphere trigger bounds, and a bit above ground. Make sure it's Probe Type is 'Distant'. Each Atmosphere trigger needs one distant probe in it, but one maximum.
Hit Level > Render all lightprobes in the menu bar up top.
Then make sure your atmosphere is actually the one showing when viewing the world in the render window:
Try to render the worldmap then, and see if it works. Otherwise I can do a write-up for you to make a custom minimap atmosphere to get roughly this result: