Does your user (with superadmin privileges) has ‘administrator’ role?
URE hides itself from other users with access to plugins list.
URE may not add menu “Users->User Role Editor” as ‘administrator’ role does not get URE’s specific permissions during plugin activation. “Deactivate/Activate back” helps usually in such rare situation.
You may make another try. Delete plugins/user-role-editor-pro folder via FTP. Open plugins list – WordPress will deactivate unexisted plugin automatically. Then try to install and activate URE Pro again.
