I cannot open the .scribe file saved in Version 3.9 in the older version 3.7? what is the way out?
VideoScribe for your desktop will always be forward compatible (projects made in older versions can be opened in new ones).
Sometimes you can go the other way too, it depends on what has been updated in the new version. If it's a completely new feature then the older versions will have no knowledge of that code and the projects will not work so those cannot go backwards.
v3.9 had a big enough update to cause that situation so projects created or edited in that version cannot be opened in older versions.