Use this command in the remote asterisk console (asterisk -rv) to force an endpoint to check config. In the example, this is for digum phones. The full listing of /etc/asterisk/sip_notify_additional.conf (commands for other phones) is listed below.

pjsip send notify digium-check-cfg endpoint <extension #>

Remove the brackets when entering the command above!
[aastra-check-cfg]
[cisco-check-cfg]
[cortelco-check-cfg]
[digium-check-cfg]
[grandstream-check-cfg]
[htek-check-cfg]
[linksys-cold-restart]
[linksys-warm-restart]
[obihai-check-cfg]
[polycom-check-cfg]
[polycom-reboot]
[sangoma-check-cfg]
[sipura-check-cfg]
[reboot-snom]
[spa-reboot]
[reboot-yealink]
[algo-check-cfg]
[snom-check-cfg]
[snom-reboot-cfg]
[fanvil-check-cfg]