The material has a shader, selecting the material may show !!MISSING SHADER!! where the shader should be.
The shader works on all our destination platforms, if you're using a custom shader, check for warnings - for space, all shaders need to work with all destination platforms. (If your shader does not work on a particular platform, we recommend using the 'Fallback' statement to fall back to a standard shader, or use Fallback Off, and the item will simply not render.)
The item is pure black and unaffected by lighting
This usually implies a shader bug (NaN and Infinity values are often rendered as pure black by most GPUs)
Uploads
My Region Fails Always
This may be a bug with the processor, we'll be looking into it anyway
Large regions may hit a maximum processing time limitation (currently set to 90 minutes.)