It’s been mentioned before in the topic here: https://forum.corona-renderer.com/ Background layer missing
But I’ve now tested to make sure it’s reproducible.
If alterations are done in Corona post processing AFTER the render has finished (in Picture Viewer). When you go to save out the layered PSD file, the background beauty pass is missing.
If you’re interested my test file is here: Unique Download Link | WeTransfer
it includes ‘test A.psd’ which i saved out directly after rendering. Plus ‘test B.psd’ which i saved out secondly after altering the tone mapping. AS you can see, in ‘test B’ the background image in missing,
Using the Corona 3 full release, C4D 20, mac, latest version of Ps.