Messages from my gmail account not importing

How do I give eMclient permission to read and write to my googlemail account?  Some old messages have been imported, but nothing current, and I can’t see any logic behind what has imported and what hasn’t.  I can see on Google pages that Thunderbird has been given third party access, so I assume I need to get to that stage with eMclient.

The registration process is described in The access permissions are given in step 5 and 6 via Google dialogues.