Some parts of model aren't being lit?

Sorry if this is a dumb question, or weirdly phrased, let me explain it better.

So I have a single model for the level with a light res of 4096, and a single light source (a directional light).
It seems some of the model isn’t being lit at all, no matter how much I tweak settings it looks like garbage:

I believe it isn’t being lit because when I toggle the ‘affects world’ tag, it look like this:

It may not come across well in two separate images, but when I toggle it, the ‘shaded’ areas in the lit image are completely unchanged from the unlit version.

I’ve been pulling my hair out trying to figure it out, and for other reasons, I can’t change the angle of the sun.
Can someone help me puzzle this out? I bet its something stupid I’ve overlooked.

Did you made UV map properly in your 3d software before export model? And after you import did you set the UV map chanel for lights to the unrapped one?
If no go back to your 3D software and unrap the model after reimport it oppen the editor and see what UV channel was unrapped and in light settings set the right chanel