Besides from allowing from Google Calendar to share data with other apps and also link the accounts from the configuration in Esential Space, only after adding a task to ES and only if it has an established time will it be synced with Google Calendar.
So e.g. if you just take a screenshot of an appointment, don’t expect for it create a GC reminder, you have to first add the task to ES and then it will sync. At least that worked for me!