Upgrading from freepbx 13 to 16

[festimbeqirii (Kosovo)]

Im upgrading the server from version 13 to 16 but the problem is when i restore the backup in the new server everything looks fine all my configuration are restored but the grandstream phones cannot connect to the sip

[dwsiemens (Dan S)]

Try
(http://your-pbx-ip/):your-pbx-webgui-port/admin/config.php?display=extensions&action=resetall