We can only process retouching orders with image files: RAW, JPEG, TIFF.
Lightroom's Smart Previews method can only be created and edited within Lightroom. A Smart Preview is copy of a photo file. This file is compressed and lossy. This is why we are able to process culling and color correction orders (in Lightroom) but not retouching or album design (Photoshop).
If you would like to submit a color correction order with file type as Smart Previews and connect a suborder for retouching, you absolutely can however once the color correction order is complete we will need you to upload the RAW/XMP or JPEG/ TIFF files for retouching to be completed.