Before starting the process, make sure that you are logged in to your Zendesk instance with the user account you wish to perform the action with, and login to the Portal in the same browser.
To refresh/revalidate your Zendesk token, access the Integrations app in your Customer Portal:
Go to Settings;
In the Translation settings card, find the 3 dots on the top right and select the option Refresh Token:
Please note that you must have a Customer Portal Admin role of either Owner, Admin, or Integrations Manager, all the while being a Zendesk Admin as well in order to see these options and for the created token to be valid.
Note: Refreshing the Zendesk Token will determine that the user completing the process becomes the new Unbabel Admin.
And voilà, we are back in business.