Have you factory defaulted the unit as described in the Admin Guide to reset the Network Settings ?
Have you checked that the Phone has been assigned an IP Address?
Have you checked that the assigned IP Address can reach the Network where the Provisioning Server is on?
Have you checked that the assigned IP Address does not contain a DHCP Provisioning Information for another Server?
You can check via a Wireshark Trace what kind of network activity is produced by the phone and what address it is trying to reach.
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