Call Display on Multicall Keys

[brogerson]

Have a single copper trunk that rings into a 5340 set. There are Multicall Keys of the main answer point on two other 5340 phones.

Call display works fine on the main phone but no call Display on the Multicall Keys on the other two set.   

Display Caller ID on Multicall/keylines is enabled,   and all three phones have the same COS.

[VinceWhirlwind]

There's a COS option called "non-prime public network identity", check if that's enabled.