Project is Invalid or Corrupt

I recently upgraded from Storyline 2 to Storyline 360.  Whenever I try to open a story file, I get the error "This project is invalid or corrupt and cannot be opened.  It may have been created in an earlier version of Storyline."  I have hundreds of courses that were created in Storyline 2 that I do not want to lose.  I have searched other posts and have done all the suggestions, but none of that works.  My temp files are deleted nightly, so that won't work either.  I'm really regretting upgrading to 360. 

Any suggestions on how to stop this from happening?  I'm scared to open my old story files as I don't want to receive that error!