Mirrors renders black in Airport Island - Villa Park

I've bought the Airport Island - Villa Park model, and i have a problem with mirrors on it... I've merfed another scene with two mirrow and when i do the render, no matter with render engine or shader i choose, the mirror renders black. It seems the relection is there but is almost imposible to see. This tow mirrors works fine in the other scene, Any clue, solution about that?

In other way, is normal that these scene, the Airport Island - Villa Park, takes about 1 hour to just start render? (i have i5 with 8gb ram, 4 gb 960 nvidia)

Thanks

Update: refections is not working on any object