UE4 solves lighting need to be rebuilt

1. Open ‘World Settings’.
2. Goto ‘Lightmass’ category.
3. Check ‘Force No Precomputed Lighting’.
4. A popup will appear. Press ‘OK’.
5. Press ‘Build All’ or ‘Build Lighting Only’. Static Lighting will be crack. That’s OK.
6. Save the map.
7. Reload the map. Open another map and open the map or double click the map in content browser.
8. Lightmaps will be 0 in Lightmass categoty. If not, load the map again.
9. Uncheck ‘Force No Precomputed Lighting’.
10. Save the map.
11. Press ‘Build All’ or ‘Build Lighting Only’.
12. Solved

Read More: