Hey There,
Thanks for writing back with a working login credentials!
Are you sure you’ve purchased the X-theme or Cornerstone? As the given code doesn’t seem to be a valid code for X-theme purchase.
Would you mind rechecking your code? You can get the code from the ThemeForest account of yours. Just go to your Account section and select Downloads. You’d see downloaded themes there along with the purchase code.
Thanks for understanding!