Lighting and shadows issues after build

I’ve been trying to figure this out for days now. I’m still very new to UE4 and fairly new to C4D but I did some modelling in C4D, created the UV maps, and managed to work past many of the initial problems that others were also having with C4D -> UE4. But now I’ve hit a wall and I’m not really sure how to fix it :confused:

That’s what happens after I build the level. I think it’s a lightmap problem because the shadows aren’t turning out. And rectangular windows create an imperfect rectangle, and for some reason it streches where the floor meets the wall.
When I’m in C4D, I have the UV’s mapped out with no problem, but once they’re in UE4, they turn to this:

Balcony:

The most difference I’ve been able to make is when I increased the lightmap size from 64 to 256. Sometimes the shadows are complete squiggles, a problem I haven’t been able to pinpoint.

Couch:

I don’t know what causes the couch to completely grey out after the build process either. Any help is greatly appreciated