Check the
Cloud Availability Center for planned and unplanned downtimes of your cloud system and
subscribe to Cloud Availability Center notifications in the
Cloud System Notification Subscriptions application.
The Cloud System Notification Subscriptions (CSNS) application makes it easy to add, customize, and manage subscriptions to Cloud Availability Center notifications.
Using this tool, SAP Cloud customers can remain constantly informed and receive timely updates regarding their SAP Cloud Services, including – but not limited to – planned and unplanned downtimes, and customer communication.

Additional task for SAP Sales Cloud and SAP Service Cloud (aka Cloud for Customer) customer:
Maintain contacts via the CSNS App to receive support, maintenance and upgrade notifications.
In Service Control Center there is a hint to use CSNS and direct links are provided:

Solution Brief
User Guide
https://launchpad.support.sap.com/#/csns
Support Portal