Green building/objects?

Hi all, I am new to UE4 and having issues when building my lighting all
buildings turn green? I have to turn off and on overridden light map res. under lighting.
Got no idea what is happening? I did not get this on my other test projects.
Help will be appreciated. Cheers

Most likely you have bad lightmap UV’s or your lightmap UV coordinate is not assigned to the correct channel.

Thanks Darthviper107, I will check and try to import my sketchup file to 3dsmax for uv’s.Cheers