In the Polycom setup, please try the following using the details generated in Terminal Password form:
a. Navigate to Settings > SIP > Line X where X is the number of the line (your choice).
b. Address: “SIP Address” also known as “SIP URI” written in form <User ID>@<SIP Server>, e.g. 515@demo.ringotel.co
Authentication
c. Use Login Credentials : Disable.
d. Domain : SIP Server, e.g. demo.ringotel.co:5061
e. User ID : This must match the Auth ID of the Terminal Password form.
f. Password : Corresponding Terminal Password.
Outbound Proxy
g. Address: Leave Empty
Server 1
i. Address : Enter SIP Server e.g. demo.ringotel.co
ii. Port : 5060 or 5061 for TLS security
iii. Expire : 3600 (1 hour)
iv. Subscription Expires : 3600
v. Register : Yes
vi. Click Save