I added some BSPs. I converted them to static meshes. I gave them basic box colliders. Their lightmap resolution is 32 (I experimented with this making it as high as 1024). I built the level, and now I have really bad lighting.
Screenshot:
Thanks.
-do you get any errors after rebuilding the light? 
-add a skylight to get rid of those black shadows
-your problem is that you dont get any shadows at all? -> make sure to set your quality settings to “epic”
-also make sure to post a picture from the level before the build
Before Build:
With Skylight default settings:
I’m not sure what the skylight was supposed to do.
I also don’t know where the quality setting is but since dynamic shadows work I don’t think that’s the problem.
I guess you didn’t change the lightmap index from 0 to 1 (the second UV channel) after converting BSP to mesh ?!
Thanks! You are my hero. Now I’m having light seep though cracks. If this is a quick fix the please reply, but I’m pretty sure I can find an answer through Google.
Change the lighting quality from Preview to Production. This will help with some seams. Depends on how the asset is setup with the UVs.
You can change the quality by going to Build > Lighting Quality > Production
You can also fine more information on the Wiki guide that Eric and I have made with common lighting questions: https://wiki.unrealengine/LightingTroubleshootingGuide#Lighting_Quality_comparison.2C_or_Production_.3E_Preview
On my directional light I turned up the DynamicShadowDistance from 0 to 30000. This fixed the light leaking. It still happens if I go far away and look back (I am not 30000 uu away) so more help here is appreciated, but I can work with this for now.
EDIT: I set DynamicShadowDistance back to zero because there’s a better solution. My lighting quality was already at production. I turned up the lightmap resolution from 64 to 512 and now the problem is completely gone.