Please ensure you always check the community FAQ and/or utilize the community search before posting any new topics or follow up post’s. In addition check the release notes.
There is a here post here:
In addition the release notes mention on page 2:
Polycom Unified Communications (UC) Software 5.5.1 is a release for Open SIP and Skype for Business deployments.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's