Hi Thomas.,
From the error that you have sent in the comments section, it seems that the Curl Support module is not enabled in your server. The curl support module needs to be enabled in your server as shown in this screenshot http://prntscr.com/dnb57f Please ask your hosting team to enable that module and then try installing the plugins.
If you still have any issues, kindly mail your WordPress and FTP Login Credentials through the right bottom form @ http://themeforest.net/user/designthemes so that we will check the issue.
