I am sure I can copy files from my laptop to App Studio Developer before but suddenly, I can't do it now. I tried many times but the files didn't show in App Studio. What's going on?

Here's a few thoughts:

1) Please check to see if anything changed in your access rights.

2) Try to copy to a shared network drive instead of directly from your local drive.

3) Add "Windows Desktop" to your AS Explorer and try it from there.

If it's App Studio 8.0.08 then you might have to quit and restart App Studio. I think this is one of the many bugs I found...

I know I couldn't find an option in App Studio 8.0.08, so I went in via the front end and uploaded my files that way into a Content Folder.

I should have said that after copying, the files don't appear in the explorer, after quitting and restarting they do appear. I think that has something to do with the Explorer view nor getting refreshed. The symptom does depend on which area the files were copied to - reporting server, Content repository or Web Applications.