Existing IP Office systems being upgraded to IP Office Release require a software upgrade license.

! Warning: Upgrade License Requirements
On a new system, when the first call is made, the software level being run is written into the control unit's permanent memory. Any subsequent upgrade to a higher release requires the addition of the Essential Edition license for the target release. Systems upgraded without that license display "No license available" on some phones and will not allow any telephony functions.

! Note: Server Edition Systems
IP500 V2A control units configured as IP500 V2 Expansion System systems are licensed and upgraded through the Server Edition web management menus. Refer to the Server Edition documentation.