Having this same problem. Seems the mix rgb node has issues. U can't plug a black and white texture to the amount pin. Doesn't work :-(
This is proving very difficult for corrections I am trying to make to a recent project.
I am suggesting Cycles till Blender issues with Corona standalone are looked into.
I have spent close to 3 whole days struggling with the nodes, why some don't work the way they should, or don't work at all. Bump/displacement is also another issue. Uv node has a bug issue as well. If you are working on a serious project especially for clients, this might pose problems down the road.
At the moment, blanchg doesn't have access to a Windows machine so suport for Corona with Blender would take some time.
