During your mail migration from Google, you’re hitting the following error:
Access Not Configured. Tasks API has not been used in project [xxx] before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/tasks/overview?project=[xxx] then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry. 
You didn’t activate the task APIs in the Google developer console.
Connect to google developer console and activate the Task api: