After a firmware update, you may need to reset your headset and EHS settings on your phone as follows:
Go to Menu > Settings > Basic > Preferences > Headset > Headset Memory
By default, it will display as Disabled. Change to Enabled
Press Back to return to Headset Menu
Go to Hookswitch Mode
Select Headset Type
Press Back to exit Menu
No reboot is required
(Note): This applies to all Polycom® SoundPoint® phones.