The authcode is the transfer code needed to transfer your domain from one provider to another.
All domains, except .ES domains, require this code to be transferred.
You can request a new Authcode for your domain from "Domains & SSL", located in the blue side menu -> Domain portfolio
Click on the drop-down menu "..." that appears to the right of the domain for which you want to request the authcode -> Request Authcode
You will be able to generate a new Authcode: