The acknowlegde function is designed to become active at midnight on the day of service. If your time zone is incorrectly set then your acknowledge function may not become active for some hours after midnight, preventing staff from using the function as intended.
If your acknowlege function is not appearing as expected (ie the check boxes are not appearing) then the first thing to do is check that your company time zone is set correctly.
To change your time zone go to
ADMIN > SETTINGS > Date & Time Settings and choose a new time zone from the drop down list.