This page gives you some hints when you get an error or run into a problem for communication scenario SAP_COM_0523 or SAP_COM_0527.
The troubleshooting on the page can be used for the products:
The value in the UI field Token Endpoint in the communication system is not correct. It must be the SAP Cloud ALM service key parameter "url" + /oauth/token
During the registration of the ABAP cloud-based system the process checks if this system was already imported into Landscape Management from SAP's Cloud Landscape Directory.
Usually, we import all cloud services of a customer automatically shortly after SAP Cloud ALM is provisioned.
The error message indicates that the cloud system doesn't exist in Landscape Management. Please check the Landscape Management Troubleshooting page for details