Pocket Informant on iOS has been syncing to Google Calendar since its inception. When we first introduced Informant we had the option of using CalDAV, ActiveSync, or Google’s Calendar API v2. Every calendar developer would tell you to use the Calendar API as it was the most robust and featured of the three. As of November 17th the version 2 of this API is being shut down.
Last year Informant version 3 introduced support for the then new Google Calendar v3 API. However if you use Pocket Informant 2.64 or below (we recently saw someone using 1.6), Google Calendar sync will no longer work. Google turned off support for the v2 Calendar API that 2.64 and below use.
If you are still using Pocket Informant 2.64 and below then you will need to upgrade to Pocket Informant 4.5 and above. Contact our support and you will get a coupon for half-off. Please note that if you are using iOS 7, 4.52 has some issues with iOS 7 that are fixed in 4.53 that is currently in review with Apple that we expect to get released this week.