Hello Omri,
welcome to the Polycom Community.
The community's VoIP FAQ contains this post here:
Oct 7, 2011 Question: Phone unable to Dial a number when Off Hook or on 2nd Call in a Conference or Digitmap issues
Resolution: Please check => here <=
Please utilzie the above to troubleshoot your issue.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Best Regards
Steffen Baier
Polycom Global Services
