ICTDIALER makes calls from 1 to 300 but it stays on almost 300 connection.

I have 1200 ports(40 E1) but it can not exceed 300 concurrent calls! any configuration should i set in FS, Plivo, Httpd or ...? i have HP G8 with ICTDIALER VM 8 cores and 16GB RAM! any suggestion guys? PLZ help me asap!

regards.