Summary

Followed the steps as per https://developers.google.com/gmail/markup/apps-script-tutorial, send an email to myself, received email looks plain - no action button visible.

Expected Behavior

I expected to see an action button in the received email

Actual Behavior

No action button

Steps to Reproduce the Problem

1. follow https://developers.google.com/gmail/markup/apps-script-tutorial
2. execute the action in the app script editor
3. view the email - there is nothing