Installation failed

Tried every methods to install the pro version (ftp, direct coping and adding zips file to in stall), the theme icon showed up, but when I clicked the live previe, I got the following error: Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator to inform of the time the error occurred and of anything you might have done that may have caused the error. More information about this error may be available in the server error log. I noticed when I use adding zip file to install the theme, the first installation success, but all the language installation failed. Please help! Thanks