App Service Deploy in release pipe line: app service name empty (throws HTTP 500)

Hi,

When creating a service connection to an app via publish profile the connection becomes visible in the release pipe line, step App Service Deploy. The app service name drop down remains empty and on the background I get a HTTP 500 retrieving the values.

In November when we created the project this worked fine. But now it does not anymore (nothing changes in the configuration).

The resource group, app and so on are all on the same subscription so I verified the most obvious. But I really have no clue as to what this can be. What can this be?