Emissive lighting doesn't always work

Hi, I have used a static mesh with emissive material to light a room and it worked well (I check ‘use static emissive lighting’ and set ‘static’ for the mesh ) but now I want to copy the mesh in an other room and it doesn’t work anymore (the room stay dark). This room is a bsp (like the first) and the only change I have noticed is that the room is a little exposed to the sun. Any ideas please?

Have you tried building the lighting?

Yes, in fact I have forgot the reflection capture so the material that I used appeared dark, thanks anyway