In version 7.83 of FAWeb, teachers are able to click on the All Present button on the homepage in FAWeb to indicate that attendance has been taken and all students were there. Clicking on this button will change it to a green checkmark. When certain teachers click this button, it shows that it's loading but it does not change to a checkmark and Attendance Taken still says No.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.