If you're currently using Google Calendar to subscribe to your Close.io Tasks Calendar you may have noticed events are not showing up right away. This is a known issue with Google Calendar's handling of third-party calendar subscriptions.
It seems there is a caching mechanism Google is using to limit the number of times they refresh external calendars -- with the side effect that Tasks within your Close.io account aren't immediately reflected within your Google Calendar.
Unfortunately, Google says: "Note: It may take up to 12 hours for changes in ICS feeds to reflect in your Google Calendar."
While there's currently no way to work around this issue by continuing to use Google Calendar, we recommend using a calendar application which does refresh calendar subscriptions properly such as Apple Calendar or Microsoft Outlook. Instructions on how to set those applications up can be found here.
For more technical and historical context on this issue there are several threads related to the issue: