The MyMaxon account will not show previous Cinema 4D Serial numbers (R20 and previous) please create a ticket at support.maxon.net to request Serial numbers and legacy installers.
As per November 2021 - Red Giant Products Purchase History and serials can be seen in the MyMaxon Account.
As per September 2021 - Redshift Node-locked Licences can be seen in the MyMaxon account.
Redshift RLM licences cannot be viewed inside the MyMaxon account
As per September 2022 - Zbrush Activation Keys can be seen inside the MyMaxon account.