Cisco 8800 Series Administration Manual page 137

Hardware and Accessory Installation
Key Expansion Module Does Not Go Through the Normal Start Up Process
• Power over Ethernet (PoE) doesn't meet the required power-supply.
• Connected number of key expansion modules exceed maximum "Number of Units".
Solution
• Change the phone to use the same type of expansion module.
• Check the PoE the phone connected to.
• Check if the unit number is bigger than the "Number of Units".
Cisco IP Phone 8800 Series Multiplatform Phones Administration Guide
121