Hello Gary,
welcome to the Polycom Community.
The community's VoIP FAQ contains this post here:
Oct 7, 2011 Question: Phone unable to send DTMF to an IVR system or how to troubleshoot DTMF issues
Resolution: Please check => here <=
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