adobe updated the project format without bothering to tell anyone, and without waiting for a new major version, and without any exports for older versions. so, you need to make sure its the same version on both computers, or at least update to the current version 8.2.0. i believe they changed the project file in 8.1
Thanks RoninEdits, but how to upgrade to 8.2.0, I have 8.0 and when i click on updates it says its uptodate, even creative cloud things says that my software is uptodate
you can try signing out and back in. if you are on mac i've seen posts here where they had to do something to fix, but i cant remember what exactly.
you can also try direct download from here