Hi PnsAle0298 •,
Welcome to Microsoft Q&A forum and thanks for using Azure Services.
As I understand, replication is failing when done through portal for Azure PostgreSQL Flexible Server with error: "Property id '' at path '' is invalid. Expect fully qualified resource Id that start with '/subscriptions/{subscriptionId}' or '/providers/{resourceProviderNamespace}/.
Could you please let us know the configuration details of the server and region in use? It might be a transient issue related to region.
Awaiting you reply, thanks.