If SIP authentication is enabled on the alternate call server, you need to enter the SIP authentication password for the target extension when you program an ESL button.
If your alternate call server is a Wave, this information is encrypted in User/Group Management and cannot be read or copied.
In order to be able to provide the SIP authentication password to the administrator on the Wave primary call server, when you create a target extension on the alternate Wave, type in and confirm the password, and then keep a record of it. (If you forget the password or there is no record of it, change the password manually and make a note of the new one.)