Hello, I'm the developer of psd-manager and just had a brief look at this using Alpha 7.2. The reason why the current psd-manager version (3.2.2) can not save the image is simply that Corona supports no 3ds max render effects, right? So psd-manager never gets the signal to save the image. Saving the main image and render elements at the render end should be doable, I will see what I can do for the future. All the other psd-manager features require support for the 3ds max G-Buffer channels and Corona does not provide those as far as I know.
Best Regards,
Daniel Schmidt
psd-manager Developer