Error 403 trying to get a list of messages and tasks with google apis (TasksV1 and GmailV1)

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VB

Task

Gmail

google-api

Hi.

I am working with VB.Net, I followed the instructions to get a list of messages (gmail api v1) and tasks (tasks api v1) from Google:

https://developers.google.com/gmail/api/v1/reference/users/messages/list
https://developers.google.com/google-apps/tasks/v1/reference/tasks/list

But I get the error 403 (Insufficient permission) but my datagridview is filled with the following headers with empty cells:

Gmail:

HistoryId - Id - LabelIds - Payloads - Raw - SizeEstimate - Snippet - ThreadId - Etag

Tasks:

Etag - Items - Kind - NextPageToken

I checked my google developer console and all is well, the apis are activated.

I also use my xxxxxxxxx@developer.gserviceaccount.com (just in case).

Also follow the instructions of Drive and Calendar apis and these work fine but of Tasks and Gmail give me that problem.

I use credentials (client id and client secret) to enter.

I tried on Google api explorer and everything works fine.

How can I fix this error?