This error indicates that the call preservation feature is active because the application has lost its connection to Cisco CallManager. The TCP session between the phone and its primary Cisco CallManager is cut. This issue is documented in Cisco bug ID CSCsa68462.
The workaround for this or any other invocation of the call preservation feature is to hang up manually. If the phone does not return to normal on-hook behavior (all lines are shown while idle, softkeys are appropriately displayed, and the phone is responsive to user input), confirm that the Cisco CallManager is not down or has failed over appropriately. If this procedure does not solve the issue, perform a hard reset. If you use an application such as IP Communicator, then restart the Communicator application.
The issue is fixed in Cisco IP phone load 7.2(3) and Cisco CallManager version 4.1(3). You can download the required phone load and Cisco CallManager versions from these locations:
If you receive the CM Down Features Disabled error message when using IP phone 7970 with Cisco CallManager running 3.3(3)sr3 or later, reboot the 7970 by pressing **#** after IP connectivity to the Cisco CallManager is verified.
This error message with the 7970 IP phone is documented in Cisco bug ID CSCed58339.
This error message is also displayed if a 7935 has a shared line appearance with another phone and the other phone is on a call when the Cisco CallManager goes down. The 7935 also shows that the Cisco CallManager is down and features are disabled. The 7935 should immediately failover to the backup CallManager because it is not on an active call.
This problem is documented by Cisco bug ID CSCdw70183.
In order to overcome this problem, after the 7935 is in this state, press the offhook key. The phone then re-registers.
CallManager 3.x, CallManager 4.x
IP Phone Models
7900 Series IP Phone, 7970G, IP conference station 7935/7936