Hello, thank you for acceptation and your help. I need it because i bought a brand new PC with windows 10, i installed audiocity 2.4 and as i wanted to work with the files i just created last week on my old Pc (surface pro microsoft), the file open from my dropbox and just close everything 3 sec after (file + soft) without any error message…i tried to unistall and intall again, same problem 
. Thanks for your help ! 
Which exact version? (Look in “Help menu > About Audacity”)
Don’t do that. dropbox can cause many weird problems due to synchronization.
Copy the file to a normal directory on your hard disk and open it from there.