I thought the paid version would allow adding a time to a task. Just read the feature list and its your highest listed feature, that hasnt been delivered for 3 years?
It seems there is an issue with your Google API, but other users have commented that other apps do allow this integration.. could you please provide an update or let us know who to speak to at Google to make this happen?
P.s not having a go at you, now I realise you are a 3rd party developer. I thought this was a Google app.