The file I created with Sim4Life light cannot be opened.

The document, .smash file, I created with Sim4Life light cannot be opened with this error message, "This document was created using the full version of and cannot be opened in Sim4Life light."
Could you tell me what problem often make this error occured and how can I resove?

Sim4Life light is specifically designed for undergraduate and graduate students to support their research and education. It can not open the files created by the full version. You can export the model from the full version of Sim4Life as a .sat/sab file and then import it in the light version.

If you don't have a full version, i think (untested) you can still recover the model by importing the smash file in the modeling tab.