Thank you very much for your feedback!
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I've tested to see it works. Please check if you have finished both steps below before syncing data from Google Cal.

Please go to the Settings page on web version: https://i.doit.im/home/#/settings/account , click two buttons:
1. Click “Link to Google Cal, which is used to sync tasks in Doit.im to Google Cal;
2. Click “Modify the reverse-synced calendar lists”, and choose a calendar of Google Cal, which you may use to sync tasks from Google Cal to Doit.im.

Having finished the above settings, you may see the two sides can sync each other’s tasks. If you want to see the latest data of Google Cal in Doit.im, just click “Sync GCal”. It’s because there are quotas for Google’s sync, that is, it is unable to transmit data automatically to other apps from time to time.

If any further questions, please feel free to contact us.
Nice day!