welcome to the Polycom Community.
It is always useful to include the currently used software version as issue experienced may already be addressed in a newer release. This also allows yourself and others to check against current software release notes.
In addition you should also specify the Polycom product you are using.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
Please share the system details. if system is HDX 4000 then disable the basic mode in call preference option.
Also enable the Firewall ports/ AES encryption/ and select Diffserv value 34 instead of Ip ip precedence in class of service option.