There was a bug in the early versions of the installer. If you update your NDP/endpoints to latest version and/or uninstall then re-install Htek Phone should be there.
Please check the setting:
In Endpoints Admin UI:
(1)Go to Configuration > Device Definitions
(2)Edit the Device Definition of an HTEK phone
(3)Set "SLA Support" to Yes
Please check the Setting:
Login webpage, and click Setting→Preference→Check-sync reboot=Enable