The Polycom desk phone could not be working for a few reasons; the phone is not connected to the internet, upgrades/updates done to the phone system, physical issues with the phone (physical buttons do not work). One of the most basic troubleshooting steps is to restart the phone. If there is a cable connected to the left (as shown in the picture below), disconnect the power cable for 15 seconds and then reconnect. If there is just an Ethernet cable going to the port that is in the red box, disconnect the Ethernet cable from the phone, wait 15 seconds, and then reconnect the cable.
If the phone issues are still not resolved, submit a ticket.