hello, new here, need some urgent help.
After i done this model, i import to lumion but i found that this part was missing. therefore i reopen again my sketch file all these part become wireframe. even i try changed layer, layout, tried everything that i can do, but still the same. any idea? i had checked the file was completed before import to lumion. even i got backup few files but all the same part become wireframe.
if possible i dont feel like redo… 
If there was a window asking for an automatic repair of your model, you should be very careful.
Are those elements components?
Do you have very little geometry in there?
Can you share the model?
Cotty’s questions are essential to provide an answer particularly if you can share the model.
If you have truly lost the faces and they are not just hidden or on a hidden layer you could however try the plug in Eneroth Face Creator. Unlike some of the other face creation plugins it will also work on components without exploding them.
https://extensions.sketchup.com/en/content/eneroth-face-creator
If that doesn’t work,as a lost resort the Sandbox tool could even be tried.
Su does not import to Lumion but rather you can export a 3d model and depending on what version of SU you have Pro or free will determine formats you can export and export options which you have not stated. 
You should have only one back up version of your file if you have that option set, but you can have a number of auto save files if auto save is set.
Have you checked the rendering mode you have set?;
If you have the free version then you can export a .dae or .kmz format but it has a number of options to slect what did you do??
Clarification would help but posting model is better.
One thing that always can be tried is to upgrade your graphics card driver, in case you are experiencing an OpenGL problem. To test for OpenGL problems, go to Window menu>Preferences>OpenGL , uncheck Hardware Acceleration and restart SketchUp. If everything now looks and works normally (albeit slowly), an upgrade or downgrade to a working display driver is in order.
Anssi
attach ur model so that other expert can also know the problem with model or with ur system
Hello guys! The issue is not longer important! Thanks for those who take time to read my issue and reply, appreciate that. 