Whole render or specific objects are white, washed out, semi-transparent, invisible, or textures are missing
---Since Corona Renderer 1.6, textures and other assets are transferred from the master PC to the nodes automatically if needed - if you are experiencing an issue similar to the one described below, please contact us at firstname.lastname@example.org ---
Solution: This usually means that some of your render nodes can't access the assets used in your scene (textures, xref objects, proxies, plugins, etc). Providing access to these assets for all of your render nodes should fix this problem. Open Asset Tracking (File > References > Asset Tracking or Shift+T) and make sure you are using UNC paths ( \\server\path\ ) instead of local drive paths ( C:\path\ ).
See: Asset Tracking Dialog on Autodesk website
You can also try using 3rd party tools or scripts to collect all the assets automatically.
Example: Asset Collector script