this option is greyed out for me. “Force no Precomputed Lighting”
Here is what fixed it for me: go to Project Settings, Engine - Rendering, and make sure that “Allow Static Lighting” is checked.
Also if for UE5.6 you will find that it gives you an error about missing swarm. You have to download UE5.5, go to the UE_5.5\Engine\Binaries\DotNET folder, and copy-paste the files in the same folder in UE_5.6, IMPORTANT: DO NOT REPLACE FILES, just paste and skip existing files.