Here is an easier way to reboot a polycom phone. No unplugging and nonsense needed.

Here’s what to press on the Polycom phone to get to the reset option:

Home -> Settings -> Basic -> Restart phone (option 7 or 9)

Note: Home button can also say "menu" or just be a picture of a house

Using hotkeys

I am usually a proponent of hotkeys, but these seem to not be as straight forward. It is an alternative way to reboot the phone though!

IP 321, 331, 335: Volume-, Volume+, Hold, and Handsfree

IP 450, 550, 560, and 650: Volume-, Volume+, Mute, and Messages

IP 6000: *, #, Volume+, and Select

IP 5000,700 and SoundStation Duo: *, #, Volume-, and Volume+

VVX 1500: Delete, Volume-, Volume+, and Select

VVX 500, VVX 600 and SpectraLink 8400 Series: 0, 1, and 3 dial pad keys.

VVX 300, 310, 400, 410: dial pad keys 0, 1, and 3 while the phone is off hook