It seems your purchase code is not valid. Please provide the purchase code that you’ve got from themeforest so that we can validate your purchase & provide support.
You’ll be able to check the purchase code from your download section checkout the screenshot: http://prntscr.com/mxt8g2
Also if you go to theme support in tf you’ll be able to see your puchase code in there. http://prntscr.com/mxt9w1