If you can sign in with the Support Panel Desktop ver 2 but is not possible with the ver 3 maybe you have a PHP configuration issue.
A conflict in the PHP configuration can cause that the Support Panel Desktop getting more information in the regular communication data that can be affect the product.
The follow is an example :
Information included by the server:
Warning: ob_start() [ref.outcontrol]: output handler 'ob_gzhandler' conflicts with 'zlib output compression' in /home/domains/public_html/components/com_activehelper_livehelp/server/services/login.php on line 2
In order to fix the conflict just have to add this to your .htaccess file:
php_value zlib.output_compression off