Access token fails to provide access to message text & metadata

Question

When I try to get information from a message, gives me an error as if access token were null:

Error with the add-on. Run time error. TypeError: Cannot read property "accessToken" from undefined. [line: 184, function: sendEmailasTask, file: Cards]

The code is:

  var accessToken = e.messageMetadata.accessToken;
  GmailApp.setCurrentMessageAccessToken(accessToken);

  var messageId = e.messageMetadata.messageId;
  var message = GmailApp.getMessageById(messageId);
  var subject = message.getSubject();
  var sender = message.getFrom();
  var body = message.getPlainBody();
  var messageDate = message.getDate();

I gave broad OAuth Scopes, but I still get the error message:

"oauthScopes": [
  "https://www.googleapis.com/auth/gmail.addons.execute", 
  "https://www.google.com/m8/feeds",
  "https://www.googleapis.com/auth/script.external_request", 
  "https://www.googleapis.com/auth/userinfo.email",
  "https://www.googleapis.com/auth/gmail.addons.current.action.compose",
  "https://www.googleapis.com/auth/gmail.addons.current.message.metadata",
  "https://www.googleapis.com/auth/gmail.addons.current.message.readonly"
],