To activate the Redshift subscription you need to ensure you are using the latest version of the Maxon App from the link below.
https://www.maxon.net/en/downloads/ - You will find a blue download button for the Maxon app at the top of the page
Then sign in with your MyMaxon account - and Activate Redshift. Licenses are now stored with your account.
There are no activation keys for the Redshift subscription.
Please note - this is compatible with 3.0.54 and onward only - it is not backwards compatible and cannot be used to license anything before 3.0.54
If you have a Redshift Node-locked licence, your licensing method has not changed and you still use the Redshift Licensing tool.
This document explains the location of the Redshift Licensing Tool.