Continuous feed of appointments to Google calendars
Currently, the Gmail calendar sync will only feed appointments present at the time of setting up the integration. It will not feed any future appointments made after that time. It will save so much time for Gmail users who have to manage 2 calendars.
We're aware of this issue - unfortunately google's implementation of iCal subscription is not amazing and they poll for updates on an inconsistent basis (more info on complaints around this here: https://productforums.google.com/forum/#!topic/calendar/HXd9eoTUOkM%5B1-25-false%5D - the thread is unfortunately still relevant today).
We may look at doing a more direct (non iCal) integration with google in the future that will get around this issue - happy to leave this open to see what the interest is like / how many users this affects.