import files "obj" In Sculptris


I just downloaded Sculptris that I find very good and easy to use. Only I encounter a major problem: I can not download OBJ files in sculptris, including the files I created in Sculptris and saved as obj. That’s why I think there is a problem.
I essentially need to rework in sculpting elements created in Rhino and vice versa to finalize a project. I tried all the possible settings from Rhino at the time of export to OBJ but it does not work.
It seems that I am not the first to meet this problem but I do not find the solution in the discussions on this subject.
This project is very urgent for me. Do you have a solution to bring me? I specify that I work in a mac environment.
Thank you for your help!