HTML5 app and SAP HANA Cloud Connector: Cannot open tunnel with id

Hello HANA Cloud Experts,

following Rui Nogueira's Blog Lightweight HTML5 apps and Git on SAP HANA Cloud Platform I wanted to try bringing my bol2rest project to the HANA Cloud but connect to a SAP CRM on-premise backend. The SAP HANA Cloud Connector is quickly installed and I was able to build a Java app that connects to the public ping service of the ABAP stack. This proves that the connection from the HANA Cloud to the on-premise backend can be established successfully.

Now I've  created the destinations in the Cockpit:

I've used this destinations in the neo-app.json file:

{    "routes": [        {                "path": "/sap/bol2rest",                "target": {                                "type": "destination",                                "name": "vcrbol2rest"                },                "description": "bol2rest Service on VCR via SAP Cloud Connector"        },        {                "path": "/vcrpublicping",                "target": {                                "type": "destination",                                "name": "vcrpublicping"                },                "description": "VCR public ping"        }    ]
}

I've pushed this file and the index.html via git, created a version and activated this version in the console. There I see that the required destinations are available:

But unfortunately when calling the URL:

https://bol2rest-s0001142741trial.dispatcher.hanatrial.ondemand.com/vcrpublicping

the following error is returned:

Cannot open tunnel with id account:///s0001142741trial

Hope someone can help on this issue.

Best regards

Gregor