The Polycom VVX range of devices DO NOT SUPPORT SSO (this statement is subject to change in the future but we are unable to specify a date).
SSO is either enabled or disable for a domain, it is not user-based. Therefore, if you wish to enable SSO for a domain, you will not be able to use user-based accounts on this domain with VVX devices.
Accounts can be created on the VIA portal and the password set for common-area devices and meeting room devices. However, users will not be able to use their own accounts to sign into devices.